Acicles

 Acicles, Prickles and Stalked glands in Wild Roses.  Photos and thoughts.

Rosa rubiginosa showing pedicle acicles and stalked glandular hairs.

Since June I have been looking at Roses. A difficult group of species which often hybridise.

As a beginner I was advised to ignore hybrids, as even separating the species is hard enough for a first year. Anything which did not fit the species description in the BSBI Handbook no7, Roses of Great Britain and Ireland, was at first given the 'walk on by' treatment. Eventually, as confidence grew,  a guess was made to the possible parents of a hybrid plant. An example was a possible hybrid between Rosa micrantha ( Small-flowered Sweet Briar) and Rosa rubignosa ( Sweet Briar) which was somewhat dependent on the presence or absence of Acicles.

This raises the question of what actually does an acicle look like?   How do you separate an acicle from a stalked glandular hair or a straight prickle?  The term acicle is applied to the rigid version on the main stems and also to the soft versions seen on the pedicle and hypanthium and this can cause some confusion.

The handbook treats acicles as a type of prickle on the stems, however in the description of Rosa rubiginosa it describes the pedicles as glandular-hispid, the glands often mixed with small acicles.

The Rose handbook description for an acicle is :-  In a few species such as R. pimpinellifolia the larger prickles may be interspersed with much smaller ones called acicles. These are often straighter than the large prickles, and may come in all sizes down to what appear to be stiff bristles.  However unlike a true bristle ( or stiff hair), acicles always taper to a point from a broad base. Occasionally acicles are gland-tipped.

P. pimpinellifolia  All prickles or are there acicles as well?

Another definition from CTW is :- Very slender prickles or stiff bristles, not stout-based, sometimes gland-tipped. Stace defines acicle as - a slender prickle with scarcely widened base.

In practice these definitions hide the fact that stalked-glandular hairs, acicles and straight prickles could be said to form a continuum. 

Location.

The acicles can be present on the pedicle/hypanthium and the flowering stems although the stem version are hard and stiff whereas the versions on the pedicle are flexible.  Maybe separate names could be used for the types of 'hair' found on the pedicle/hypanthium vs stem.

R. rubiginosa hypanthium and pedicle (flower stem).This photo shows the longer non glandular acicles and the shorter glandular stalked hairs.

The above photo of R. rubiginosa clearly shows two types of hair. 

Glandular hair. Some are clearly stalked glandular hairs with the gland being of a size that forms a large ball whose diameter is several times that of the diameter of the hair tip, on which it rests.  

Acicle. The second type of 'hair' is generally longer, has a thicker tapering body and usually ends without a glandular tip.  I have regarded these as acicles. Occasionally these acicles have glandular tips but these are often not balls but just darkened ends. One feature is that the very base of these acicles is not enlarged by any great extent unlike a prickle. 

Since acicles are a feature of R. rubiginosa and are not seen on R. micrantha or the Downy roses like R. sherardii it might be worth looking at examples of pedicle/hypanthium hairs on these species.

R. sherardii  23rd September, West Cork.

The point of this photo is to show that no acicles are present which is what you would expect, but that the length of the stalked glandular hairs can include very long ones. Length cannot be used as a determining feature in distinguishing acicles from glandular hairs.

R. micrantha, 12th June, Cambridge.

 The above photo shows Small-flowered Sweet Briar with stalked glandular hairs and no acicles which conforms to the expected species description. These glandular hairs do not appear insect friendly.

R. rubiginosa. 14th October , Croydon.

The glandular tips are deteriorating rapidly turning white at this time when the fruit are going soft.  This photo shows how difficult it can be to distinguish between the stalked glandular hairs and the acicles which can be the same length. The lower right 'hair' had a large ball of sticky chemical whereas the one going left looks as if it just terminates in a point and is therefore a acicle.  The complication is that glandular hairs can lose their glandular tips and acicles can occasionally have glandular tips with a ball shaped gland on.

R. rubiginosa 14th Oct  Croydon.

A feature of R. rubiginosa is the unequal prickles on the stems.     This photo shows the variation of dense prickles, many of which are thin and narrow pointed and might be regarded as acicles. The more typical curved prickle is shown in the next photo which is part of the same plant. This variation in the shape of the prickles is typical of rubiginosa. 

 

R. rubiginosa 14th Oct Croydon showing more typical shaped prickles.

R. rubiginosa , stem just below pedicles

The descriptions in the literature do not clearly differentiate between an acicle and a straight thin prickle. I would regard the prickles on the main stem as thin prickles since they have a elliptical base. Strangely some have a tiny glandular tip. This is an example of the intermediate characteristics that  occur. The conflict in the description about the base being either wide or not wide, from the Rose handbook, CWT and Stace, adds to the confusion. My thought is that it's the shape of the base rather than the width, that to me seems to separate prickles from acicles.

14th Oct Hybrid R. micrantha/rubiginosa 

The above photo shows an acicle with three stalked glandular hairs. The glandular tips are deteriorating at this late stage. All have slightly wider bases but this is limited compared with a true prickle. 

 

Example of accicle with round base on stem just below pedicles.

Stalked glandular hair on hypanthium ( R. tomentosa)

Intermediate in that the base appears somewhat elliptical but tiny glandular tips are present.

A straight prickle, based on its elliptical base. 

Fig 1. Possible difference between stalked glandular hairs, acicles and narrow straight prickles.

 Length is variable although acicles are often longer than stalked glandular hairs on the pedicle/hypthanium. Bases can be smaller than shown as proportions are for short versions.

Glandular hairs sometimes lack the glandular tip and acicles occasionally have glandular tips. Surprisingly even straight prickles have been seen with glandular tips on one occasion so all three types are not absolute in their features. Approximate colouring is late season, hairs and acicles are green at flowering time. Prickles are rigid when mature, acicles and stalked glandular hairs remain flexible on the pedicle.  Acicles have a tapering tip, sometimes darker or occasionally a glandular ball which might be slightly smaller than usually seen on adjacent stalked glandular hairs.  Since no absolute difference is 100%, check more candidates on the plant to determine the presence of acicles.  

With roses, no rule is 100%, so careful consideration has to be given to the complete range of features.  

I have avoided using the term 'pricklet' as in the handbook it is used to describe the smaller prickles that occur on the petiole and rachis ( leaf stems).  

Pricklet on rachis

Another term used is bristle, which is used in place of acicle in Harrap's wild flowers.

Peter Leonard   Rampton     18th October 2020

Please comment if you can add anything to this possible interpretation or let me know if I have misunderstood the literature.  The rose season is just about over so it will be next year before I can learn more about this difficult group. 

 

Reference:-  Roses of Great Britain and Ireland by G.G. Graham and A.L. Primvesi, BSBI Handbook No 7.

Leaf edges in Cambridgeshire Roses

Leaf edges in Cambridgeshire Roses.



On the 3rd June I had zero knowledge of roses. A chance encounter with Rosa micrantha (when looking at Crested Cow-wheat), initiated a quest to see and photograph all the possible rose species to be found in Cambridgeshire.

The main problem with wild roses is they all hybridise with each other and I took good advice to ignore hybrids, at least to start with.  I looked for pure examples of each species, based on the principle that I need to learn the features of each basic species, before one could even consider examining hybrid plants. This involved rejecting examples which did not conform exactly to the handbook description.

I ordered Sell and and Murrell Volume 2 which arrived on the 5th June. This volume contained somewhat disturbing news, quote ' We support John Lindley's remark of two hundred years ago that the study of Roses has been so detailed that one can no longer distinguish species. They are in a taxonomic and nomenclatural mess. All we have been able to do is follow Graham & Primavesi's (1998) Roses of Great Britain for species and hybrids, but we believe that this is a dumbing-down which produces aggregates that could be ecological and geographic non-sense'.

Roses of Great Britain and Ireland, BSBI Handbook No7 by Graham and Primavesi would appear to be a very good starting point despite the rather negative comments by Mr Sell.
Over the summer I have managed to photograph the possible species to be found in Cambridgeshire using the handbook No7 as a guide, in an attempt to find 'pure' non-hybrid examples. Actually all the roses are derived from hybrids and what are regarded as species are just stabilised and widespread plants that share the same features. The BSBI handbook is well laid out, has good line drawings and is concise covering species and hybrids and remains the essential reference text. More recent Dutch work still uses much of its content.

This blog shows leaflet edges of the species and compares them with the stated description in the handbook, as either uni-serrate, bi-serrate or multi-serrate.

Handbook descriptions are stated for each species and the photos compared to see if they agree with that description. Definitions from handbook :-

A) A Uniserrate  leaflet has sharp teeth, all more or less the same size.

B) Biserrate is defined as having large teeth, from the lower side of each of which a single smaller tooth arises.

C) A Multiserrate leaflet has large teeth, on the lower side of which, and sometimes also on the upper side, two or more smaller teeth arise, these secondary teeth being usually gland-tipped. This type is not as well defined as the previous ones, because in some cases the secondary teeth are little more than rounded protuberances tipped with glands, and the larger primary teeth are sometimes not noticeably sharp-pointed.


One immediate problem when looking at leaf edges is that there is variation even on a single leaflet, which for example may have uni-serrate teeth on one part and bi-serrate on another.

1) R. arvensis Field Rose

Temple dome shape with base convex and concave point.

R arvensis leaflet tip showing dome shape teeth with the tips having a hydathode.

Described as crenate-serrate. Crenate means rounded. The hydathode is a hard red tip, not glandular.

Dome shape only present towards tip of leaflet.

This is not a clear cut difference but pure R. arvensis tends to have the dome shaped teeth at least on the sides near the tip. Other species share this temple dome shape but the convex base is often not quite as pronounced. Burnet Rose also has these temple dome shaped teeth but it does not occur wild in Cambridgeshire. Some Dog Rose and hybrids also show this dome shape. 

A R. arvensis  that does not show this shape might well not be pure. Those with occasional stalked glands would suggest some influence of some other species. Note also the example above has some bi-serrate sections which are less temple dome shaped.

R. tomentosa

Dog Rose

2) R. stylosa Short-styled Rose

Described as uniserrate. R. stylosa  shares the dome shaped teeth but not as perfect as in R. arvensis.

R. stylosa showing Uni-serrate edges

Hydrathodes only , no stalked glandular hairs should be present.

3) R. Canina agg.  Dog Rose

Example of a Dog Rose with red tips ( hydathodes) only without any glandular tips. The secondary tips when probed were hard and did not show the normal soft sticky balls that glandular tips have. They seem to be hydathodes rather than glandular hairs. This leaf edge could be regarded as bi-serrate with alternate main teeth and secondary smaller teeth.

Example of a Dog Rose ( possibly a hybrid with R. stylosa) with red tips plus some stalked glandular hairs. This edge might actually fit the description of a bi-serrate edge with its primary teeth and smaller secondary teeth..
Dog Rose is an aggregate of several different variations. The additional problem in Cambridgeshire, is that the Northern Dog Rose R. cassia has hybridised with R. canina and these hybrids are the most common (but variable) plants to be found.

Dog Rose showing that different parts of a leaf may have a different types of edge.

R. canina can have uni, bi and multi serrate leaf edges depending on type although so far I have not found a example with a multi-serrate edge ( group Dumales)

4) R. obtusifolia now called tomentela  Round-leaved Rose.

Described as finely biserrate with numerous small, reddish-brown glands on the teeth.
The glands tend to have formed their own tips giving a multi-serrate appearance but note the glandular tips tend to occur on only one side of the main teeth. This might just about pull the description back to being biserrate. Tricky as the clear sides main tooth edge has a single glandular tip on three of the teeth seen in this photo against only two which have no secondary teeth. Secondary teeth, number two rather than the single tooth as suggested in the description of bi-serrate. I think these definitions are starting to struggle with this leaf edge. I would call this multi-serrate because the glandular hairs are generating tips of their own and not just formed straight onto the edge. 

This example has glands on the underside but this feature is lacking in several of the Cambridgeshire sites.

R. obtusifolia 22nd June Burton End, Cambridgeshire 

This example has very round leaflets but this does not guarantee a obtustifolia as hybrids can have same rounded shape. The edge appears very spiky as the teeth are quite narrow.

R obtusifolia.  5th July 2020 Gamlingay Wood.

The small leaflets have some tendency towards a bi-serrate edge but it is not consistent. Leaflet shape not quite so round but still typical, with lots of overlap and hairs on both sides.

R. obtusifolia except middle hybrid leaf.  4th August Gamlingay Wood

R. obtusifolia except middle hybrid leaf.  4th August Gamlingay Wood

Many plants are hybrids Rosa canina x obtusifolia ( R. x dumetorum) so it is quite hard to find examples that really fit with Round-leaved Rose 100%.  The leaflets overlapping is probably more important than the rounded shape which is present in some of the hybrids. R. obtusifolia leaflets tend to have a dark shinny green surface with at least some white hairs on upper surface although canina agg. can have some white hairs on upper surface but normally limited to near the mid-rib. Not an easy species to nail down and not common at all in Cambridgeshire. Most of the plants at Gamlingay Wood were not 100% conforming to the required feature set of Round-leaved Rose, but a couple of plants on the east edge did seem to fit.

5) R. rubiginosa Sweet Briar

Described as strongly glandular-biserrate.  This photo above does show a bi-serrate edge. A second leaf photo below does show this with primary teeth and slightly smaller secondary teeth. It is certainly strongly glandular.

Glandular hairs are stalked and often do not form tips on leaf edge.

The bi-serrate edge  is clear  with many glandular hairs on the edge which rarely form a point of their own. R micrantha seems to have glandular hairs that form tips but at a low density, but a much larger sample of plants would be needed to see if this feature is consistent and it's a very subtle difference given the leaf to leaf variation. Whereas R. rubiginosa seems to have a bi-serrate edge, R. micrantha seems to lack this being multi-serrate. Probably not a reliable difference but worth looking for.

6) R. micrantha Small-flowered Sweet Briar

Described as glandular multi serrate. I would agree as the glandular hairs are often forming their own tips  but the quantity of glandular hairs is quite low with typical just one on the leading edge and two on the trailing edge.

R. micrantha showing glandular hairs on tips.

R micrantha showing sparse glandular tips without stalks.

7) R. tomentosa  Harsh Downy Rose

Described as irregularly biserrate.
Underside of leaflet very hairy with white matted hairs. Edge has red tipped hydathodes on the teeth tips and the teeth sides have short stalked glandular hairs which are mostly formed on small teeth of their own. Zero to a maximum of three glands per trailing edge tooth side. The leading or clear edge of each primary tooth in this case has no glandular hairs.
 Biserrate is defined as having large teeth, from the lower side of each of which a single smaller tooth arises. It is a fine distinction to multi-serrate. In this example the primary large teeth are dominant whereas the next species examples of multi-serrate edges, the secondary glandular tips make the primary teeth less dominant.
This is partly down to tomentosa having fewer glandular tips.
Note the lack of tiny glandular on the underside leaf surface which are hard to see at the best of times but appear to be missing in many R. tomentosa in Cambridge. Sometimes a few leaves have the tiny stalked glands whereas as many lack them on the same plant. Due to the hairs on both sides of the leaflet it can be hard to see the margin clearly but in conclusion I would say the leaf edge is bi-serrate to multi-serrate so irregularly biserrate is not far off.

8) R. sherardii  Sherard's Downy Rose.

Described as glandular-multiserrate.
Red hydathode tips as usual plus glandular short stalked hairs on tiny teeth (most of the time) do give a multi serrate look to the leaflet edge.   Between one and four glandular hairs per main tooth side. Glandular tip quite variable in size. A rather messy edge.

R. sherardii  1st September 20  Fourwentways. Cambridgeshire

9) R. agrestis Small-leaved Rose

Described as glandular-multiserrate.  The tips have the usual red hydathodes  and short stalked glandular hairs which are on the sides of the teeth without forming a separate tip of their own.  One to four glands occur on each side of the tooth. In some ways the leaflet edge is uni-serrate with additional glands as these glands only have formed on tiny teeth of their own to a very limited extent.
Without this level of magnification the leaflet edge would look glandular multi serrate. No clear edge of the main teeth appears with secondary glandular teeth on both sides although the shape indicates the right hand edge is the clear one which on average also has less glandular hairs. The leaflet tip will be to the right, indicated by the clear edge being on the right hand side.

R. agrestis 22nd August 2020 

Conclusion.

The descriptions for bi- and multi serrate  are tricky. This is recognised in the description on Multi-serrate in the handbook and I suppose the authors were somewhat constrained by previous work.
The think the main problem is due to the glandular hairs either just being on the leaflet edge or forming a point on their own. If the point is large you get the multi-serrate appearance even if the basic leaf edge is uni-serrate or bi-serrate. The example above for R. agrestis has a basic uni-serrate edge with all primary teeth the same size. The glandular hairs are mainly not forming any tips and the few that do are tiny. Because the glands are quite large in the field this edge would look multi-serrate but when enlarged and looked at in this level of detail a better description might be uni-serrate with additional glands. And that is before we consider variation.

I can't say I have found any new insights into separating these species but I am now at least more aware of the current descriptions and will pay more attention next season. Hydrathodes are solid whereas glandular hairs have a ball of sticky stuff at the tip but as the glandular hair ages it will lose some of its stickiness so that it can be hard to tell them apart unless examined under a microscope. As ever, you can't name a rose by only looking at its leaves, as all features have to be examined.

Peter Leonard
23rd August 2020
Rampton
Cambridgeshire.

Update  More pictures of R. micrantha.

R.  micrantha  28th October 2020. Castle Camps, Cambs.

R. micrantha  20 Oct 20 Langley Wood, Cambs

Forget-me-not. How hard can it get?

Forget-me-not. How hard can it get?

Wood Forget-me-not Myosotis sylvatica, Rampton, 18th April 2020

When you consider dry habitat Forget-me-nots there are only four common species to consider. The field guides indicate that the flower size may be the key identifying feature however the dimensions of the flower may not be adequate to distinguish one species from another.  A quick check in the more serious literature emphasises this point, especially if you are (un)lucky enough to find a plant with flowers that are not the standard size e.g. sylvatica var. sylvatica.
Species considered here:-

Wood Forget-me-not           Myosotis sylvatica                           Flower size  8-10mm dia.
                                            Myosotis sylvatica var. sylvatica                      4-8mm dia.
Field Forget-me-not            Myosotis arvensis                            Flower size  1.5-6mm dia.
Changing Forget-me-not     Myosotis discolor                            Flower size  1-3mm dia.
Early Forget-me-not            Myosotis ramosissima                     Flower size  1.5-3mm dia. 

To quote Sell and Murrell. m arvensis, ramosissima and sylvatica run into one another and are difficult to distinguish on precise characters but usually be recognised in the field when all taxa involved have become familiar.  Well that's reasonably hopeful but then quotes Arthur Chater who says "In Cardiganshire, pollen size is the only reliable difference between M. ramosissma and M. discolor."
Pollen size is well beyond me so,  I just though I will put up a few photos from Cambridgeshire and see what we find.

This all started due to a potted up sample of Erophila developing three tiny Forget-me-nots which required identification. These three unexpected plants were small and the flowers were also small.  I have never really looked at Forget-me-nots before so it seemed a good 'lock down' activity. Wood and Field Forget-me-not also grow in the garden.

Wood and Field FMN are both common so I will start with that pair.

M. sylvatica is really a garden plant and has large flowers typically 8-9mm across.  It is planted and it escapes. Field FMN M. avensis is the poor relation with much smaller flowers.  It is interesting to note that apart from the flower size, the other dimensions of the pedicel and stem are much the same for both species.
The pedicel is slightly longer that the length of the calyx.  The calyx of the Wood FMN are open in fruit whereas the tips of the calyx are almost touching in Field FMN.  This is apparently a good feature but just how reliable it is after the comments by Sell is to be seen. The angle of the pedicel from the stem is not reliable.

Field FMN left, Wood FMN Right

Apart from the size difference, the point of this photo is to show how the stem terminates in a fine display of 3-5 open flowers in both species.  The flowers emerge from a ammonite like spiral at the stem tip in Forget-me-nots.  The flowers start off pink and change to blue when open. The Yellow ring called the 'Fornice' at the base of the petals changes to white as the flower ages.

M. avensis Field Forget-me-not showing spiral of forming flowers.

Note the pink petals on the flower just about to open. The calyx holding the corolla tube is very hairy with hooked ends.  All the species considered here have these hairs. Also note the stem and pedicle have hairs that lie flat. They start patent ( at right angles) and turn through 90 degrees very quickly to lie against the stem.

M. arvensis showing all pink petals.

This plant has forgotten to change its petals to blue, uncommon but a well known variation.

M sylvatica Wood FMN showing stem hairs near flowers are flattened onto stem.

The above photo of Wood FMN showing the spiral of flowers which is much the same as in the previous photo of the Field FMN apart from the size of the flowers.

M. sylvatica, upper stem hairs

M. sylvatica Stem hairs

M arvensis, upper hairs

M. arvensis Stem

Again the stem hairs in both species seem the same with lower stem hairs being long and patent and upper hairs being flattened.  The leaves have long simple hairs on both sides plus on the midrib. No veins are visible. The leaves have no stalk. The leaves are alternate.

Calyx hooked hairs.

M. arvensis calyx

M. sylvatica calyx  

Disregard the red colour in the photo of M. sylvatica above, the red is from the background now removed and since the hairs are transparent it shows the background colour.  The hairs from the base to just over halfway are curved to the point of being hooked. Outer hairs are straight. The hairs in M. arvensis do in general appear to be longer and more dense than in M. sylvatica. The tips of the calyx tend to be close together in M. arvensis and open in M. sylvatica , but this is not always clear cut and may be dependent on whether nutlets are present.

M. arvensis  

M. sylvatica Fewer shorter hooked hairs.

As far as the two species growing in my garden are concerned,  separation by flower size is easy. The problem comes with  larger flowered versions of Field Forget-me-not, being occasionally recorded usually associated with woodlands. According to Alan Leslie, in the new Flora of Cambridgeshire, these large flowered versions are regarded as equated to subspecies .umbrata  and have a different chromosome number 2n=66 ( 2n=36,48,52 is reputed for subspecies arvensis).

Field Forget-me-not ( M. arvensis) growing in poor soil on the Fleam Dyke can have small flowers, down to a diameter of 1.5mm.

Field FMN. Very small flowers from Fleam Dyke

The situation with Wood Forget-me-not , M. sylvatica is also complicated by a variant  M.sylvatica.var sylvatica  which has flowers 4-8mm wide and is regarded as the original wild type.  There is a another larger flowered variation var. cults with flowers 8-11mm which is usually a garden escape. These garden escapes can have bright blue flowers and also white flowers are not unknown.

I would conclude that any examples with intermediate size flowers would present quite a challenge since the open vs. closed calyx in fruit might not be 100% reliable?.  This is where secondary features like the density of hooked calyx hairs come in.

Unfortunately the nutlet shape  is not a reliable indicator of species as some M. sylvatica have nutlets with only a tiny rim, being much the same as M. arvensis. The other factor is that as the nutlets dry out, their shape changes.

M. sylvatica left, M. sylvatica var. sylvatica middle, M. arvensis right.

The Wood FMN M. sylvatica flowers are about 8mm across , the var. sylvatica 5mm and the Field FMN M. arvensis about 3mm although they can be smaller.  These intermediate sized flowers would be easy to miss and identification depends on the calyx being open or closed and the density of the calyx hooked hairs. In this case the combination of calyx being open and the dense hooked hairs suggested M. sylvatica var.  sylvatica.  


Early Forget-me-not Myosotis ramosissima.

M. ramosissima Upper stem and flowers. No spiral, only two more buds hidden. (Isleham potted plant)

The standout feature of the three plants in the pot is that the flowers are tiny.  They were measured at just under 1.5mm across. The plants are also small being 50mm high with either one stem leaf or no stem leaves. The hairs within the inflorescence stem are appressed and lie pointing upwards.

M. ramosissima. Flower less than 1.5mm diameter. Isleham site. Potted

The flower has the same fused petals ( just at the base) , and the yellow fornice, just like the larger species but the petals are very pale with limited blue towards the outside and a white base.

M.ramosissima.  Cambridge

M. ramosissima, Cambridge. Fruiting calyx are open.

M. ramosissima.

The plants from Isleham now potted up (with my Erophila) have paler flowers than the Cambridge site.
They both have fruiting calyces that are open so you can see the seeds developing.  The three potted plants do not show the spiral of new buds. In the first photo two more new buds are hidden from view, becoming the tip of the stem. See below.

M. ramosissima tip of flowering stem. (Isleham Potted)

This lack of a multi-flowered spiral seems to be a feature of some Early FMN but other have a spiral similar to Changing FMN.  The above photo shows two flowers open and only two new buds forming. 

A limited sample from only one site and the Wild Flower Finder site
https://wildflowerfinder.org.uk/Flowers/F/Forgetmenot(Early)/Forgetmenot(Early).htm  has photos showing that some plants have more buds than others.  It would seem that M. ramosissima can also have the spiral of buds.

Myosotis ramosissima ssp. ramosissima

Changing Forget-me-not showing extent of spiral with 14 buds.

The flowers of M. ramosissima often point upwards but M. discolor point downwards and horizontally and are often fading by the time they start to point upwards. 

M. ramosissima nutlets,  no rim, convex both sides.       

Top, Early FMN , below Field FMN M. arvensis.

Note the thin stem ( 1mm) and short pedicels on the Early FMN as well as the small flowers. A much thinner plant that given good growing conditions can grow quite tall. Generally seems to have fewer leaves than Field FMN. Tends to only display one or two open flowers that keep their yellow fornice.      

M. ramosissima. Fen Drayton. Note open calyx and short pedicles.

This plant has two stems, basal leaves only, no stem leaves and at this stage was only about 5cm high.

Changing Forget-me-not M. discolor  

Two sub-species are present in the UK , however whether they are easy to separate or they merge is yet to be investigated. They do have different chromosome numbers.
M. discolor ssp. discolor 2n=72
      Upper stem leaves nearly opposite. This applies only to the leaves at the base of the secondary      flowering stem only and some plants seem to lack this feature however it is worth looking for opposite leaves on other stems..
      Caylx is bell shaped with teeth not converging in fruit. Not sure about this bell shape.
      Yellow corolla at first 1.5 - 4mm across. Some are bright yellow but others are pale with just a touch of yellow. Flower colour does seem to be a distinctive feature of these two sub-species. 

M. discolor ssp. dubia 2n=24
      Upper leaves alternate at the point where a secondary flowering stem joins the main stem. In other words, the leaf at that junction is not matched with another leaf on the other side of the stem. 

Calyx is pear shaped with caylx teeth converging in fruit. Not sure about pear shape being much help.

Cream or white corolla at first without any yellow tinge.

M. discolor ssp. dubia.  Fen Drayton, Cambs. Single stemmed small plant.

 

M. discolor ssp. dubia. A very large plant growing in a shaded damp place and over 30cm high.

M. discolor ssp. dubia with the single leaf indicated, not having an opposite leaf.

       

The following photos show discolor ssp. dubia. Note how the leaves can come  up the stem on some plants unlike in M. ramosissima which has a longer inflorescence.

M. discolor, Cambridge showing white flower emerging.

The Changing Forget-me-not shares the same small size of the Early FMN with tiny flowers.

(  M. arvensis is often a large plant but sometimes can be tiny when growing in poor soil, so a plant an inch high with flowers of diameter 1.5mm can one tricky as it has the same structure with leaves well up the stem. It will show the longer pedicels which is a key feature to separate M. arvensis from M. ramosissima and M. discolor. An example is shown later.)

As the name suggests the flowers change colour as they open which is not uncommon in all these species but the difference is that they change colour after they have fully opened. They open being white or yellow and change to pale blue then darken. The internet shows examples that remain yellow or white so there is variation in unusual cases.

M. discolor ssp  dubia with open white flower. Stem hairs flattened to upper stem. Long patent hairs
on lower stem and leaves.

M. discolor ssp. dubia

M. discolor ssp dubia Note yellow fornice ring stays yellow.

M. discolor nutlets , no rim, convex both sides

Nutlets will not distinguish between Early and Changing Forget-me-nots, both have the same shape.

As nutlets dry out they can show a rim on one side but I don't think this is a reliable feature.

M. discolor ssp. discolor

M. discolor ssp. discolor showing pale yellow corolla. 13 May 21, March

M. discolor ssp. discolor showing calyx tips apart however ssp. dubia tips are often not very different.

This example does seem to conform to the literature but others are not so clear cut.

M. discolor ssp. discolor opposite leaves at upper stem junction.

M. discolor ssp. discolor upper stem junction not showing opposite leaves.

Not all plants of subspecies discolor at Whitemoor Prison, March,  showed the expected opposite leaves so this puts into doubt how reliable this distinction in the literature is. There is also the complication of a leaf within the inflorescence being regarded as a bract not a leaf so the exact rules will need more investigation.

 The 'discolor group' of Myosotis is very different from all the other species found in Europe in that it has a much larger pollen size *and several species/sub-species exist including M. balbisiana and M. persoonii ( 2n=48  twice ssp. dubia). M. discolor ssp. discolor is thought to be a hybrid and that might explain why its features are variable.

*ref http://phylodiversity.net/rwinkworth/publications/files/3.pdf

Conclusion. These four dry habitat Forget-me-nots are not quite as easy to separate as the field guides suggest and variation in flower size between Field and Wood requires careful attention to the calyx hooked hairs in order to conclude the identification in intermediate flowered plants.

In Cambridgeshire with a very limited sample it would appear that Early FMN (M. ramosissima) has flowers that start blue and stay blue until they fade and Changing FMN (M. discolor) has flowers that open when pointing slightly downwards and then change colour from either white or yellow to become blue, then are fading by the time they are pointing vertically upwards.  Structure can be a difference between M. discolor and R. ramosissima, where M. discolor has a short length of inflorescence compared with a long leafed stem whereas M. ramosissima has a long inflorescence compared to a shorter stem with few leaves. More to learn about this tricky group as some plants do seem to break the expected rules stated in the literature.

Peter Leonard
Rampton July 2020

end.
Updated May 13th 2021 with additional photos and improved comments on difference between the two versions of M. discolor and the structure differences between the species.

Plant Structures.

1) M. arvensis

M. arvensis. 7cm high plant with single stem showing upward pointing flowers, long pedicel and  lengths of leafy stem and inflorescence. This is not a typical plant but chosen as its very small flowers could mislead into thinking this was a M. ramosissima.

2) M discolor ssp. discolor.

M. discolor ssp. discolor showing primary stems have opposite leaves where they join.

Second example without opposite leaves at main junction.

M. discolor ssp. discolor.

The second example with four stems shows that where the two main stems join, only a single leaf is present. Stem 2 has a junction with four flower showing which might be regarded as the start of another inflorescence and opposite leaves so although the main site for opposite leaves does not hold true it may be that looking around the stems will show other sites for opposite leaves, see below.  A similar situation occurs in the lower stem on the right where a junction displays opposite leaves.  A final point about these structure photos of discolor ssp. discolor is the few stem leaves. Also note the very short pedicles, a feature shared with M. ramosissima. 

Close up.

Enlarged from the plant shown above, a junction that displays opposite leaves with four flowers without an obvious stem. 

3) M. discolor ssp. dubia.

Sub-species dubia showing no opposite leaves. 

The inflorescence will get longer as the flowers develop and the spiral straightens. The number of stem leaves varies from just one to four on this plant and they do not go far up unlike some dubia plants.  

M. discolor ssp. dubia  All alternate leaves. King's Dyke.

Different population and different structure with alternate leaves held close to vertical stem before flowering shoots spilt off high up.  

Summary.  To separate M. discolor into sub-species discolor and dubia, first check first the colour of the newest flower to open, before it changes colour. If white or pale cream you have a dubia, if slight yellow is present or if you are lucky bright yellow then you have a discolor.     Next look for any opposite leaves which may occur at the junction of the second stem or even at other stem junctions.  This has not been seen in dubia but one plant from the Booker site in Cambridge had almost opposite leaves at a junction so the chances are, this feature is subject to interpretation. 

M. discolor ssp. dubia, Booker site, Cambridge

How much displacement does a opposite leaf have to have before it becomes alternate?  I regard this as not opposite but it takes a close look.

 The calyx tips are slightly more separated in discolor but I think this is too marginal a feature to be useful, unless you really have a good eye for it and a lot of magnification.

Dubia may have slightly more stem leaves but again this is tricky.