GENERA OF GRASSES OF THE UNITED STATES. 247 



Panicum glaucum L. (Sp. PI. 56. 1753), on which was based Pen- 

 nisetum glaucum, was itself based on a citation from the Flora Zey- 

 lanica (Panicum spica te^eti, involucris bifloris fasciculato-pilosis L. 

 Fl. Zeyl. 18. 1747), which refers to the species afterwards described 

 as Pennisetum typhoideum. Linnaeus described two varieties of 

 Panicum glauwm, these being now called Chaetochloa viridis and C. 

 lutescens. Through an error the name Panicum glaucum has been 

 applied by nearly all botanists to the latter species. When the 

 species was transferred to Setaria and to Chaetochloa the error was 

 perpetuated. Robert Brown transferred Panicum glaucum to Pen- 

 nisetum but used the name in the erroneous sense, as is shown by his 

 description. Nevertheless, Robert Brown must be credited with the 

 name Pennisetum glaucum even though he described the wrong 

 species. The only species of Pennisetum found native in the United 

 States is P. setosum (Swartz) Rich. (fig. 150), of tropical America, 

 which extends into southern Florida. Two species are cultivated 

 for ornament. * Pennisetum villosum R. Br. (P. longistylum of flor- 

 ists, not Hochst.) is a slender perennial 1 or 2 feet tall with a pale 

 feathery head 2 to 4 inches long, the bristles 1 to 2 inches long. 

 Pennisetum ruppelii Steud., fountain grass, with beautiful pink or 

 purple nodding spikes, longer and more graceful than those of the 

 preceding, is used for borders. An African species, Napier grass 

 (P. purpureum Schum.), has been tested recently in the Southern 

 States as a forage plant. It is a coarse perennial 8 to 12 feet tall. 



126. CENCHETJS L. 



Spikelets solitary or few together, surrounded and inclosed by a 

 spiny bur composed of numerous coalescing bristles (sterile branch- 

 lets), the bur globular, the peduncle short and thick, articulate at 

 base, falling with the spikelets and permanently inclosing them, the 

 seed germinating within the old involucre, the spines usually 

 retrorsely barbed. 



Annual or sometimes perennial, commonly low branching grasses, 

 with flat blades and racemes of burs, the burs readily deciduous. 

 Species about 25, in the warmer parts of both hemispheres, but chiefly 

 in America; 7 species in the United States, chiefly in the south- 

 ern portion. 



Type species: Cenchrus echinatus L. 



Cenchrus L., Sp. PI. 1049, 1753 ; Gen. PI., ed. 5, 471. 1754. Linnaeus describes 

 five species, C. racemosus, C. capitatus, C. echinatus, C. tribuloides, and C. fru- 

 tescens. The reference in the Genera Plantarum is to Panicastrella Mich. 31, that 

 is, to plate 31 of Micheli's Nova Plantarum Genera, published in 1729. The ac- 

 count of the genus Panicastrella is on page 36. The two species here described 

 are cited as synonyms by Linnaeus, under Cenchrus echinatus and C. tribuloides, 

 both being based on descriptions in Sloane's History of Jamaica. The first 

 species, C. echinatus, is chosen as the type. Cenchrus racemosus is now referred 

 to Nazia ; C. capitatus to Echinaria. Cenchrus frutescens, of which there is no 

 specimen in the Linnaean Herbarium, is uncertain. It is stated to come from 

 America, but this is a misprint for Armenia, as is shown by the second edition of 

 the Species Plantarum, 



