THE NORTH AMERICAN SPECIES OF PENNISETUM. 



By Agnes Chase. 



INTRODUCTION. 



The genus Pennisetum is one of that series of Paniceae in which 

 sterile branches of the inflorescence are modified into an involucre 

 subtending or surrounding the spikelets. This series falls into two 

 groups, one in which these reduced branches or bristles remain on the 

 common axis, the spikelets falling alone, the other in which the one 

 or more free or coalesced bristles fall with the spikelets inclosed and 

 aid more or less in the dispersal of the seed. The first group con- 

 tains ChaetocJiloa and its allies, the second Chamaeraphis, Para- 

 theria, Penniseium, Plagioseium, Odontclytrwm, and Cenclirus. The 

 second group is but poorly represented in the Western Hemisphere. 

 Only the monotypic genus Paraiheria Griseb., about 20 species of 

 Penniseium, and 15 of Cenclirus are native to America. 



One species of the genus, Pennisetum glaucum, pearl millet, has 

 been cultivated since before the dawn of history and is unknown in 

 the wild state. Its grain forms an important article of food in 

 Africa and to a less extent in India. In our Southern States pearl 

 millet is grown for forage. Another African species, Pennisetum 

 purpureum Schumach., is being introduced as a fodder plant in the 

 South under the name Napier grass. Pennisetum ruppelii Steud. 

 and P. macrostachyum (Brongn.) Trin., with beautiful feathery 

 panicles, are cultivated for ornament. 



The American species of Pennisetum have been much confused. 

 A recent work on the derivation of pearl millet, 1 by Paul Leeke, is 

 devoted in part to the other species of the genus. A key to all 

 the species is given and the numerous synonyms are referred to the 

 species and varieties recognized. Except in the series Penicillaria, 

 which includes " Negerhirse " (Penniseium glaucum), no descriptions 

 are given, save in new species and new varieties, and in a few other 

 instances, and no specimens are cited. The American species were 

 not well understood by Dr. Leeke, as shown by his referring the 

 American P. seiosum and the very different P. multiforum Fourn., 

 both perennials, to the East Indian annual, which he calls P. indicum 

 [P. polystachyum (L.) Schult.]. 



1 Untersuchungen liber Abstarumung und Heimat der Negerliirse [Pennisetum 

 americanum (L.) Schum.] von Dr. Paul Leeke. Zeitschr. Natunv. 79: 1-108, with 

 plates. 1907. 



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