The seeds of Nassella trichotoma (Nees)Hackel, a potentially noxious w
eed of Argentinean origin, were studied and compared with those of Arg
entinean representatives of the tribe Stipa (Stipa. Piptochaetium, Nas
sella). It was found that the other species studied could be readily s
eparated from N. trichotoma using the characteristics of the florets.
A table summarizing the important features of each genus and a key for
identifying N. trichotoma among the other Nassella species are presen
ted.