ON ALYSICARPUS RUGOSUS D. C. AND ITS ALLIED SPECIES.
L. J. Sedgwick, F. L. S.
It is a well-known crux whether the extremely diverse forms of Alysicarpus which show a lomentum with the joints deeply and closely transversely rugose belong to one species or several. De Candolle (Prodr. I, 353) described two species, — A. styracifolius and A. rugosus. Wight and Arnott (Prodr. I, 234) gave three, viz., A. styracifolius of De Candolle, and two new ones of their own, — A. Wallichii and A. Heyneanus. Baker (F. B. I. II, 159) reduced all previous descriptions and all known specimens to one variable species, for which he retained the name A. rugosus D.C., making A. styracifolius D.C. and A. Heyneanus Wt. & Arn. varieties, along with a third variety ludens from the specific A. ludens of Wallich, and regarding Wight and Arnott's A. Wallichii as a synonym of the type. Later floras (so far as known to me) have followed Baker, several other varietal names, however, having been added, viz., minor and pilifer both of Prain, and probably others.
While not denying that many of our Indian species need reduction, being merely local or edaphic forms, I am disposed to think that the Indian Floras have often on the other hand given a wholly exaggerated impression of morphological variability (as opposed to plastic reaction to environment) through failure to detect the definite characters dividing closely allied species ; and this would seem to be the prevalent view at the present time. In particular I am convinced that where in the same habitat two clearly distinguishable forms exist side by side and do not merge they must necessarily be true species. For this reason the field worker is an indispensable complement to the herbarium systematist, inasmuch as he is able to observe the innumerable plants around him, and note their demeanour.
The fact that A. rugosus D.C, as understood since the F. B. I., contains more than one species has been forced upon me by field observations at various camps in the Dharwar District during the last three seasons. For instance this winter on the black soil east of Hubli, M. S. M. Ry., two quite distinct plants were abundant as weeds in the fields. Their differences amounted to at least six characters.