Colorado Weed Seeds 
23 
1. Sandbur, Bur-grass 
(Ccnchrus L.) 
Spikelet with an involucre of rigid, connate (united) spines or barb-like 
prickles; lemma and palet less hardened than in Panicum; lemma not 
Fig. 13. Sandbur (Cenchrus tribuloides). 
Spiny involucre (left) x 5, caryopsis (right) 
X 9. 
inrolled at the margins, falcate (scythe-shaped) ; curved and flat, tapering 
gradually. 
Sandbur {Cenchrus tribuloides /.., Cenchrus Carolinian us Walt.) (Fig. 
13). — Spikelets flattened, oval in shape, 4 to 5 mm. long, armed with stiff, 
stout prickles 2 to 5 mm. long. 
2. Panic Grass, Witch Grass 
i Panicum L.) 
Lemma parchment-like, awnless, hardened, veins indistinct; margins of 
lemma inrolled ; palet similar to lemma in texture, the margins firmly clasped 
by the inrolled lemma ; seeds 1 mm.-3 mm. long rarely 4-5 mm., .5-1 mm. wide. 
Ivey to Species 
Seeds 1-1.5 mm. long, .8-1 mm. wide, oval in shape 1. .p. capillare 
Seeds 2. 5-2. 8 mm. long, .8-1 mm. wide, tapering abruptly from 
the middle of the seed to the tip 2..P. virgatum 
1. Witch Grass, Old Witch Grass {Panicum capillare L.) (Fig. 14). — 
Seeds flight green-yellow to j^ellowish oil green, shiny, obscurel.v five-veined. 
Fig. 14 Witchgrass (Panicum capillare). 
T ruits (left) enclosed in glumes, fruits 
(right) without glumes, x 9. 
colors were determined by comparing 
with the colors in Ridgway’s “Color Standards 
a number of seeds, of each species, 
and Color Nomenclature’’. 
