92 



GRAMINEAE (GRASS FAMILY^ 



1. TRtPSACUM L. GAMA GBASS. SESAME GRASS 



Spikelets unisexual, 

 tinuous rhachis above ; 



46. T. dactyloides. 



Part of spike x 1%. 

 9 Spikelet embedded X 1. 

 ? Spikelet freed x 1. 

 cf Spikelet x 1. 



ixillary spikes solitary 

 Vug. FIG. 46. 



the staminate spikelets in pairs at the joints of the con- 

 the pistillate spikelets solitary, embedded in each oblong 

 joint of the cartilaginous thickened articulate rhachis 

 below in the same inflorescence, which terminates the 

 culm or its branches ; glumes of the staminate spikelet 

 subcoriaceous, the first dorsally flattened, the second 

 boat-shaped ; the first lemma often empty, meinbrana- 

 ceous with a hyaline palea, like the second which 

 incloses a staminate flower ; first glume of pistillate 

 spikelet ovate, at length cartilaginous and closing the 

 recess in the rhachis, second boat-shaped, coriaceous ; 

 florets 2, the lemmas and paleas hyaline, the lower 

 sterile, the upper pistillate. Tall stout perennials from 

 very thick creeping rootstocks, with broad flat leaves, 

 and terminal and axillary spikes separating spontane- 

 ously into joints at maturity. (Name from rplfieiv, to 

 rub, perhaps in allusion to the polished spike.) 



1. T. dactyloides L. Culms 1-2.5 m. high ; leaves 

 3 dm. or more long, 1.5-3.5 cm. wide ; spikes 2-3 

 together at the summit, when their contiguous sides 

 are more or less flattened, or solitary and terete ; 



, Moist soil, Ct. to Kan., s. to Fla. and Tex. July, 



2. ROTTBOELLIA L. f. 



Spikelets in pairs in the excavations at the nodes of a cylindrical articulated 

 axis ; one sessile and perfect, the other pediceled, sterile, with its pedicel adnate 

 to the rhachis ; glumes of the perfect spikelet awnless, the 

 first coriaceous and covering the excavation in the rhachis, 

 the second thinner, boat-shaped ; sterile lemma empty or 

 with a rudimentary flower, and, like the lemma and palea, 

 hyaline ; glumes of sterile spikelet membranaceous. Peren- 

 nials with flat narrow leaves, and single cartilaginous spikes 

 which disarticulate at maturity, terminating the stem and 

 branches ; chiefly subtropical. (Named for Prof. C. F. Rott- 



boell, an excellent Danish botanist, who wrote 



much upon Gramineae, Cyperaceae, etc. ) 



1. R. rugbsa Nutt. Culms tufted, com- 

 pressed, 6-12 dm. high ; sheaths " flattened ; 

 leaves 5-10 mm. wide ; spikes 2-7 cm. long, 

 the lateral ones on short clustered branches in 

 the axils, often partly included in inflated 

 sheaths ; first glume of fertile spikdet trans- 

 versely rugose. (Manisuris Ktze. ) Low pine 

 barrens, Del. and southw., near the coast. 

 Aug., Sept. FIG. 47. 



2. R. cylindrica (Michx.) Torr. Culms 

 terete from a short rootstock ; leaves 2-3 mm. 



wide ; spikes slender, usually curved, 5-15 OH. long, terminating 

 the culm, on elongated axillary peduncles; sterile spikelet rudi- 

 mentary : first glume of fertile spikelet obscurely pitted longi- 

 tudinally. (Manisuris Ktze.) Prairies, Mo. and southw. June-Aug. FIG. 48. 



3. ERIANTHUS Michx. WOOLLY BEARD GRASS 



Spikelets in pairs, one sessile, the other pediceled, along the articulate and 

 readily disjointing rhachis, both alike, perfect; glumes suln-qnal. firm-membra- 

 naceous, the first dorsally flattened, more or less bicarinate, the second keeled 

 above ; sterile lemma empty, hyaline, awnless ; fertile lemma with an awn 1-2 cm 



47. R. rugro.-a. 

 Base of inflorescence 



Part of same with fer- 

 tile and pediceled 

 sterile spikelet sep- 

 arated x -2. 



Fertile spikelet x '2. 



Its flower removed 

 x2. 



Lemma x 2. 



S. K. pvlimlrica 

 x~2. 



