Dear George and Georges,

actually already Grassmann in his Wörterbuch on the very first page has taken aMSu- as the name of the plant:

„Name der Pflanze, aus welcher der Somasaft gepresst wurde...Also:1) Somapflanze,..".

For a discussion of the word and related terms and also for further references to the literature, see my article
"Rigvedische Lichtaufnahmen: Soma botanisch, pharmakologisch, in den Augen der Kavis"
(Electronic Journal of Vedic Studies (EJVS) 13-1, April 2006, 1-93.) p.22ff,
for a discussion of all the colour attributes of Soma, that are clearly not metaphoric in the RV,
p. 31-37, and for the effects of Soma which are not ephedrine-like, pp. 44-71.

Rainer Stuhrmann