Genus 22. 



GRASS FAMILY, 



1. Cenchrus tribuloides L. Bur-grass. 

 Hedgehog-grass. Fig. 396. 



Cenchrus tribuloides L. Sp. PI. 1050. 1753. 

 C. macro cephalus Scribn. Bull. U. S. Dep. Agr. Agrost. 

 17: no. 1899. 



Culms at first erect, up to i° tall, later elongated, 

 trailing and much-branched; sheaths glabrous, ex- 

 cepting the ciliate margin, compressed, very loose, 

 the upper one often partly enclosing the inflores- 

 cence; blades flat or complanate, smooth and gla- 

 brous, 4' long or less, 2"-4" wide; spikes stout, i'-2' 

 long; involucres 5-12, the body 3"-4" broad, pubes- 

 cent with very long hairs, the spines usually 2i"-4" 

 long; spikelets 3"-3i" long, not exserted beyond 

 the involucre. 



■ In sands along the coast, Long Island and New Jersey 

 to Florida and Mississippi. Bear-grass, Sand-spur, 

 Sand-bur. Aug. and Sept. 



Cenchrus carolinianus Walt, 

 grass. Fig. 397. 



Small Bur- 



Cenchrus carolinianus Walt. Fl. Car. 79. 1788. 



Culms at first erect, later prostrate and forming mats, 

 8'-2° long or more, branched ; sheaths glabrous, except- 

 ing the ciliate margin, compressed; blades 2i'-s' long, 

 2"-4" wide, smooth or rough, usually flat; spikes 1/-3' 

 long; involucres 6-20, the body rarely exceeding 2I" 

 broad, pubescent with relatively short hairs, the spines 

 1 i "-2" long; spikelets 3"-3$" long, usually not ex- 

 serted beyond the involucre. 



In dry sandy places, Maine to Wisconsin and California, 

 south to Florida and Mexico ; also in the Bahamas and 

 tropical America. Figured for C. tribuloides L. in our first 

 edition. June-Sept. 



23. ZIZANIOPSIS Doell & Aschers. in Mart. Fl. Bras. 2: Part 2, 12. 1871. 



Tall aquatic monoecious grasses, with long flat leaf-blades and paniculate inflorescence. 

 Spikelets i-flowered, the staminate borne at the top of the branches, the pistillate at the 

 base. Scales 2, nearly equal, membranous, the outer one in the pistillate spikelets broad, 

 acute and bearing an awn. Stamens 6. Styles united. 

 Grain nearly globose, the pericarp readily separable. 

 [Name in allusion to the resemblance of this grass 

 to Zisania.] 



A monotypic genus, of temperate and tropical America. 

 Type species : Zisania miliacea Michx. 



i. Zizaniopsis miliacea (Michx.) Doell & 

 Aschers. Zizaniopsis. Fig. 398. 



Zisania miliacea Michx. Fl. Bor. Am. 1 : 74. 1803. 

 Z. miliacea Doell & Aschers. ; Baill. Hist. PI. 12 : 293. 



1893. 



Culms 4°-lS° tall from a long and creeping root- 

 stock, robust, glabrous. Sheaths loose, glabrous ; 

 ligule 4"-7" long, thin-membranous; blades 1° long 

 or more, J'-i' wide, smooth, glabrous ; panicle dense, 

 i°-ii° long, narrow; branches erect; staminate 

 spikelets 3"-4" long, the outer scale 5-nerved, the 

 inner 3-nerved, both acute; pistillate spikelets about 

 3" long, the outer scale about equalling the inner, 

 bearing an awn I "-3" long, scabrous, 5-nerved; 

 inner scale 3-nerved, acute. 



Swamps, Virginia to Ohio (according to Riddell), 

 south to Florida and Texas. June-July. 



