As per efi thread :
According to Dr. Almeida's 'Flora of Maharashtra', the pods of D. triangulare are 2 - 2.5 cms. long, slightly curved, indented on both sutures, more deeply on the lower one, joints 3 - 6, as broad as long, slightly pubescent. Whereas in D. umbellatum the pods are 4 - 5 cms. long, sparsely silky when young, glabrous when ripe, thick and coriaceous, almost turgid, not reticulately veined, indented on both sutures, joints 4 = 5 [usually 4], 8-6 cm [?]    

Here's something from Dr Almeida's Fl of Maharashtra which describes the plant in the image very clearly:
Desmodium triangulare (Retz.) Merrill,
Flowers" 20 or more crowded in dense axillary peduncled umbellate heads, peduncles 3-4 mm long"....

and also from Fl of Mah, the other plant I think you are talking about:
Desmodium umbellatum (Linn) DC
"Flowers in axillary peduncles 6-12 flowered umbels, peduncles 8-12 mm long"....etc

Desmodium triangulare (Retz.) Merr. (syn. of Dendrolobium triangulare (Retz.) Schindl.)ShrubWestern Ghats, Moist Deciduous ForestsFlora of Tamil Nadu, VOL. I, 1983Coimbatore, Nilgiri, Theni, Tirunelveli

Botanical name Synonyms Family Common name
Dendrolobium triangulare Hedysarum triangulare, Desmodium triangulareFabaceae Triangular Horse Bush
Dendrolobium umbellatum Desmodium umbellatum, Hedysarum umbellatumFabaceae Horse Bush

Forest Plants of Eastern India By Amal Bhusan Chaudhuri (1993- Details with Keys-
Mansfeld's Encyclopedia of Agricultural and Horticultural Crops: (Except ... edited by Peter Hanelt, R. Büttner (2001)- Details-

I have updated eFI (efloraofindia) pages on Desmodium, Codariocalyx, Dendrolobium, Dicerma, Hylodesmum, Phyllodium & Tadehagi

Attempts have been made to incorporate most of the species available in India & nearby areas with details & keys directly or through links as far as possible. It’s quite possible that there may be some discrepancy in the accepted names & synonyms taken from other links.

Species discussed so far in efloraofindia are given at the bottom of the page in the form of links against Subpages. On clicking them one can see all the details.

Any comments/ corrections are welcome.