TEIPSACUM. 203 



spikes assume a whitish appearance; and around the 

 great lakes and larger rivers. A vile and troublesome 

 weed. 



63. TRIPSACUM— L. Gama Geass, Sesame Grass. 

 gejS'eric character. 



Spikelets monoecious, in jointed spikes, which are 

 staininate 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 ihner 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 



