TRIPSACUM. 203 



spikes assume a whitish appearance; and around the 

 great lakes and larger rivers. A vile and troublesome 

 weed. 



63. TRIPSACUM L. GAMA GRASS, SESAME GRASS. 



GENERIC CHARACTER. 



Spikelets monoecious, in jointed spikes, which are 

 staminate above, and fertile below ; staminate spike- 

 lets 2, sessile at each triangular joint of the narrow 

 rhachis, forming a 1-sided and 2-ranked spike longer 

 than the joints, both alike, 2-flowered ; glumes cori- 

 aceous, the lower (outer), 1-nerved, the inner one 

 boat-shaped ; palets very thin and membranaceous, 

 awnless ; anthers turning orange or reddish brown 

 opening by 2 pores at the apex ; pistillate spikelets 

 single, and deeply imbedded in each oblong joint of 

 the cartilaginous thickened rhachis, occupying a 

 boat-shaped recess, which is closed by the polished 

 and cartilaginous ovate outer glume, the inner glume 

 much thinner and pointed, 2-flowered the lower 

 flower neutral, palets very thin and scarious, point- 

 less ; styles united ; stigmas very long (purple) his- 

 pid ; grain ovoid, free ; culms stout and tall, solid, 

 from very thick creeping rootstocks ; leaves broad 

 and flat. Spikes axillary and terminal, separating 

 spontaneously into joints at maturity. 



Name from tribo, to rub, perhaps in allusion to the 

 polished fertile spot. 



1. T. Dactyloides (Gama grass or Sesame grass). 

 Stout, coarse, and hardy, although not considered of 



