Peas and clovers part-2.


In part one 'A look At Peas and Clovers' we looked at the basic biology of certain members of the Pea family characterized by their flowers and seed pods. We continue this theme in part-2,with a look at other species commencing with the Kidney vetch

Illustration of the Kidney vetch

Public domain Courtesy of Wikipedia.

Kidney vetch. Anthyllis vulneraria.

In this species there are two or three interesting differences in the flower parts. The calyx is inflated and tubular,and so avoid waste of material, the petals all have long claws,however, such an arrangement in a low growing plant leaves the honey exposed to small creeping insects that may well enter the calyx. 

To guard against this occurrence the calyx is covered by a woolly down and even the leaves are covered by silky hairs to discourage them. Another advantage of the tubular shape of the flower is that only long-tongued bees can reach the honey. 

Common Rest harrow Onionis repens.

Courtesy of Kristian Peters   CC BY-SA 3.0 License.

Common Rest harrow. Oninos spinosa.

Though of similar structure,this species does not produce honey,therefore there is no free stamen,because there is no necessity for leaving an opening to the staminal tube. yet the flower is fertilized only by bees even though there is  no honey the attractive flower is still a magnet for them. The rosy tint and large size of the flower lures them to seek something they will not find. The thrifty females do,however, collect the pollen,so do get something for their trouble.
there are two forms of this species,one more or less prostrate and is covered with sticky pungent hairs, the other erect not sticky or foetid, but armed with spines.
The different strategies are there to see, the low-growing one is offensive to creeping things,while the erect one with its spines offensive to browsing animals. The spines that protect led the ancient Greeks stating that no animal but an ass was foolish enough to attempt to eat it,so they called the plant ononis which became their genus name.

Dyer's greenweed.

This member of the family has a detailed account on the page of that name in the content banners above. Click on the relevant box and scroll down to view.

Honey bee on a Lucerne flower.

Courtesy of Ivar Leidus   CC BY-SA 4.0 International License.

The Medicago genus- 

In this genus the flowers are honeyed and therefore one of the stamens is free to allow access to the honey. Each wing petal is united to the keel by a couple of processes, one pointing forwards and the other backwards,and locking into a depression in the keel. These points are most easily seen in the cultivated Lucerne or the Purple Medick.

Medicago sativa ssp sativa is the Lucerne sometimes referred to as Alfalfa,and because of its large flowers,which can only be operated upon by the Bumblebee. The irritability of this species is located in the staminal tube and on this being excited by the bees tongue, the staminal tube and pistil are violently curled up to the standard,and the pollen showered over the bee, whilst the keel and wings become perminantly depressed.

Should no Bumblebee arrive, the flower does not open  and self-fertilization takes place. The pods of this genus are spirally coiled but differ among themselves to the number and closeness of the coils. Those of the Spotted Medick Medicago maculata, which was once recommended as a fodder plant,are so sharp and so numerous that cattle often refused to feed in the fields where they grew.[ Edward Step 1917}.  The Meliots,Melitotus, have small honeyed flowers which tend to droop in long racemes. Their general behaviour is much like that of the Sainfoin. {see part-1}

Barbut's cuckoo bee on white clover flowerhead.

Courtesy of Ivar Leidus  CC BY-SA 4.0 International License

Dense flowerhead species.

Most of the species that we have reviewed in part-1 and so far here in part-2 have loose flower head arrangements. Now we move on to the very dense compact heads of the clovers {Trifolium}. A novice who has been confronted with a clover plant and a pea plant both in full flower might well be pardoned for his failure to see a near relationship between the two.

yet if one pulls the flower head carefully to pieces and examines a single flower from this group,he will find that all the essential parts is like that of the pea,but the petals form a tube specially adapted to the long tongues of certain insects. Some of the flowers such as those of the Red clover,Trifolium pratense and the White clover,Trifolium repens, appear  to depend upon some special insect for fertilization.

To Illustrate this point Charles Darwin in his book 'The Origin of the Species' , told of how he expermented with bees and clovers to ascertain how far the latter were dependent upon the former for fertilization, he wrote---" Twenty heads of  the Dutch {white} clover yielded 2,290 seeds but twenty other heads protected from the bees produced not one" Again 100 heads of Red clover produced 2,700 seeds, but the same number of protected heads produced not a single seed. Bumblebees alone visit the Red clover as other bees can not reach the nectar.

This brings us to the fact that Bumblebees are very important insects as far as pollination is concerned. Should the Bumblebees disappear or become very rare the Red clover {and many other flower species} would become extinct or very rare.

The Dutch or White clover is largely pollinated by Honeybees. However, experiments have shown that if they are excluded from the plant it is not absolutely infertile,though it sets very few seeds. This would  seem to suggest that individuals exhibit a tendency to revert to self pollination.

The flowers are clustered in the heads borne on a common stalk,which is four to five inches high {12.5 cm , but every separate flower has its own tiny stalk of which it makes important use. All the flowers stand erect,and the outer or lower ones of the cluster mature before the upper and inner ones. Then as the bee pollinates them they bend their tiny stalks,and the flower begins to dry up round the swelling ovary  and to hang down round the common stalk. In this way the fertilized flowers never stand in the way of the virgin flowers,thus when a bee revisits the plant it knows to visit the erect virgin flowers, which on being pollinated will themselves bend down to the common stalk, this process will continue until every flower on the head is bent fully downwards towards the common stalk. 

Trifolium repens image taken at Mauli Pulechu. The fertilized flowers are clearly seen bent back towards the common stalk,while the virgin flowers are still held erect.

Courtesy of Forest& Kim Starr    CC BY-SA 3.0 License.

Clovers continued.

As mentioned in part-1 , the roots of the clover bears many nodules produced by nitrifying organisms, so that a field that has been cropped with clover is rich in nitrogen,and farmers find it particularly advantageous to follow clover with a crop of wheat.

Other  species of clover include the Hare's foot Clover ,Trifolium arvense, these flowers which occur in June until September are soft and downy,elongated to form a bottle-brush-shape,and occur on long stalks. They often have a pinkish tinge,with pale-brown, pointed teeth on the sepals which are masked by a covering of long white hairs. The leaflets are narrow and slightly toothed. They grow in dry grassy places and are commonest in southern and eastern England. They are absent from most of Scotland and Ireland. When in fruit the brown teeth of the sepal tube spreads widely.

ZigZag clover,trifolium medium, is somewhat similar to the red clover with notable differences. The flower heads are borne on a stalk which raises up above the foliage while those of the red clover are stalkless. The red clover has foliage which often has a clear white V-shaped band, those of the Zigzag clover the band is absent and the leaflets are much narrower. The main stems of the Zigzag clover Zigzag along their length giving rise to its common name.

There are other species of  clover but these are much rarer and very localized. 


A full bodied view of Trifolium arvense the Hare'sfoot clover

Courtesy of Cody Hough  CC BY-SA 3.0 License

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Dyers Greenweed.

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