Ischcemum. GRAMINEJE. 261 



Sacramento and oIspwIipi-p ; found as a wpod nnarly all over Enropn and tlin T^^nitcd States. The 

 closely n'liit(>(l .S'. virulh, Hcniiv., is also a ooininon weed and may he cxiMvtcd to orriir in Cali- 

 fornia; it dillers fioni the above in its j^reen color, shorter bristles, and tfie aljscnce of the trans- 

 verso wrinkles to the perfect lloret, wiiieli is striate lenfjthwise and dotted. 



S. CAUDATA, Hocni. & Schult., almndant from the Rio Grande westward, was collected by tho 

 lyes Colorado Expedition, and may be met with in the eastern counties. It is about two feet 

 high, with a long narrow spike, which is often nodding and usually nuieh interru[tted below. 



S. Califouxica, Kellogg (Proc. Calif. Acad. i. 276), was described from a specimen collected 

 in Shasta, said to have been 10 to 12 feet high. In his account of it. Dr. Kellogg says that it is 

 " i|uite similar to ,S'. Ha/iai and .S'. Grrnymiai." As so striking a grass as to size has not been 

 found l)y later collectors, it seems jirobable that he was misinformed as to its being ii native, and 

 that it was introduced without becoming established. 



4. CENCHRUS, Linn. Bur-Grass. HEDOEiroo-GRAss. 

 Spike simple, tlic flowers inclosed in an involucre at length coriaceous and bristly 

 or spiny, containing one to live two-flowered spikelets, with one floret abortive as in 

 Panicnm. Glumes two, membranaceous, the lower small (sometimes wanting), tho 

 upper 3 - S-nerved and more or less shorter than the florets. Lower floret stami- 

 nate or neutral, with one or two palets ; the lower acute or acuminate, 5 - 7-nerved. 

 Upper or perfect floret lance-ovate, acute ; lower palet somewhat chartaceous, closely 

 embracing the upper. Scales none. Stamens 3. Ovary oblong : styles 2, united 

 below ; stigmas somewhat plumose. Grain oblong, smooth, free. 



A small genus, mostly tropical, extending on this continent to the temperate regions. Culms 

 inostly branching. The inllorescence surrounded by involucral scales united below, and forming 

 when mature a head wliich is often hard and spiny. 



1. C. tribuloides, Linn. Culms from an annual root, 1 to 2 feet long, ascend- 

 ing : leaves linear, flat : spike of 2 or 3 heads, or oblong of 8 to 20 erect or spread- 

 ing spherical usually whitish heads, which are wedge-shaped at base, 2 to 4 lines 

 long, covered with spreading barbed more or less downy short sj)ines, and contain- 

 ing 2 or 3 spikelets. — C. spinifex, Cav. Icon. v. 38, t. 4G1. C. 2)aHc?JJo7-us, Benth. 

 Bot. Sulph. 5G, a few-flowered form. 



Sandy localities, from New England westward, especially on the margins of lakes and rivers. 

 It is a troublesome weed, as the spiny lieads, parting readily from the stem, cling to clothing 

 and to the bodies of animals, and it should be exterminated in sheep-raising districts especially, 

 as it fastens itself most tenaciously to the fleece and diminishes its value. It is known in dif- 

 ferent parts of the country as Hedgehog-, Bur- and Cockspur-(Jrass. The form called C. pnuci- 

 fioriis was originally collected in Lower California and since on Carmen Island by Dr. Palmer. 



C. MVosuROiDES, HBK. (Nov. Gen. i. 115, t. 35), grows in Sonora and eastward and may 

 be expected in the southern part of the .State. It is a robust erect species, 2 to 6 feet high, with 

 a narrow spike 3 to 5 inches long, of small densely imbricated heads with erect spines and con- 

 taining but a single spikelet. 



5. ISCH^MUM, Linn. 

 Inflorescence in a simple articulated spike. Spikelets in pairs at each joint of 

 the rhachis, one sessile, the other pedicelled ; sessile spikelet much flattened, im- 

 bricated, 2-flowered, the lower floret starainate, the upper perfect: pedicellate spike- 

 let (in our species) reduced to a single abortive flower consisting of but one glume. 

 Glumes unequal, the lower and outer larger, chartaceous or somewhat coriaceous, 

 5 - 9-nerved ; the inner 3 - 5-nerved, sometimes awned. Florets completely in- 

 closed ; palets very thin and hyaline, the upper sometimes very small or none, the 

 lower palet of the upper floret sometimes with an awn. Stamens 3. Styles 2, 

 distinct. Grain inclosed in the palets but free. 



A genus of a dozen or more species, ehieny Asiatic and Australian, a few being found in tropi- 

 cal America and Africa. The genus is by some included in AndropcKjon. 



