PANICEH 187 
222. Cenchrus L.—Sand-bur. Bur-grass. Low often 
weedy grasses, usually annuals, the spikelets, singly 
or 2 or 3. together, inclosed by a bur formed of 
coalesced bristles or 
branchlets, these 
usually retrorsely k 
barbed. The burs are 
borne in a spike or 
raceme, and, detach- 
ing easily at maturity, 
are transported by 
animals. The spikelets 
remain permanently 
inclosed in the bur, 
germination of the 
seed taking place 
within it. The first 
glume is much _ re- 
duced, sometimes 
wanting. The com- 
mon sand-bur of the 
United States is Cen- 
chrus carolinianus 
Walt. (Fig. 27). The 
one with larger burs 
found among the sand- 
dunes of the Atlantic 
seacoast is C. 
tribuloides L. 
223. Stenotaphrum 
Trin—The  best- 
known species of this Fic. 27. Cenchrus carolinianus. Upper 
: portion of plant with inflorescence, X%; 
genus is the St. — spikelet, x7. 
