S6 TRIANDRIA. MOXOGYNIA. 



been considered a Scirpus (Michaux), by many a Cyperus 

 (Willdenow), and Vahl has decribed it as a Schceiu/.s,- it 

 certainly approaches the genus Cyperus, but is disnn- 

 g-uished from it by the presence of tlie germinal fila- 

 ments, and its subulate glumes. In habit it very widely 

 recedes from Scirpus and Schcemis, and all the glumes, be- 

 sides tlieir very peculiar form and mode of aggregation, 

 are uniformly fertile. 



Species. 1. D. spathaceim. 2. Canadense. (This genus 

 is peculiar to the United States.) 



54. TRICHOPHORUM. Persoon. 



Spikelets nearly ovate; Calix scales imbri- 

 f ated on all sides. Corolla 0. Germinal setse 

 (invohicelliim) capillary, mostly 6, in the ripen- 

 ing seed, growing out very long. 



Culm triquetrous, leafy, terminated by a paniculate 

 umbell; or naked, with a single spike; involucellum of the 

 seed capillary and definitely parted, (seiae about 6) not 

 woolly and indefinite as in Eriophorum, to which genus 

 the T. alpiimm and T- Hiidsonianum have hitherto been 

 referred. The T. cyperhunn has a very near affinity to 

 the genus Scirpus, where it was placed by Michaux, and 

 from its great dissimilarity of habit with the Eriophorum 

 a /pi num, now referred to Trichophorum by Persoon, we are 

 obliged to consider the present genus as very arbitrary 

 and artificial. All the species'of Trichophorum, naturally 

 belong to the genus Scirpus, and there is no line of sepa- 

 raiion, except we are to consider the elongation of the se- 

 71 'ludji laments or involucellum, as a solitary character, suf- 

 ficient to constitute a genus; for the number of the setae, 

 6, so carefully inserted in the generic character, is the 

 prevailing number in the genus Scirpus. (Mr. Pursh adds 

 setis 6-9.) 



Species. 1. T. cy peri num. 2. Hndso7iianum, (nearhal- 

 lied to the Erinphorum alpiiium — only 3 or 4 inches high, 

 with a solitary spike.) 



Considered as a genus, the most remarkable of its spe- 

 cies is the T. cyperinum, confined to North America, but 

 extending from Canada to Florida; the T\ Hudsonianum, 

 if merely a variety of tlie T. alpinum, is common to the 

 sub-alpine regions of Europe, and North America. 



55. ERIOPHORUM. (Cotton-grass.) 



Scales of the calix chafTy, imbricated on all 

 sides in a spike. Corolla 0. Sad surrounded 



