GENERA OF GRASSES OF THE UNITED STATES. 
247 
Panicum glaucum L. (Sp. PI. 56. 1753), on which was based Pen- 
nisetum glaucwn, was itself based on a citation from the Flora Zey- 
lanica (Panicum spica tereti, involucris bifloris fasciculato-pilosis L. 
Fl. Zeyl. 18. 1747), which refers to the species afterwards described 
as Pennisetum typhoid eum. Linna?us described two varieties of 
Panicum glaucum, these being now called Chaetochloa viridis and O. 
lutescems. 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. Cenchrus 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 eehinatus L. 
Cenchrus L., Sp. PI. 1049, 1753 ; Gen. PI., ed. 5, 471. 1754. Linnaeus describes 
five species, C. racemosus, C. capitatus, C. eehinatus, C. tribuloides, and C. fru- 
tescens. The reference in the Genera Plantarum is to Panicastrella Mich. 31, that 
is, to plate 31 of Michel i'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 eehinatus and C. tribuloides, 
both being based on descriptions in Sloane's History of Jamaica. The first 
species, C. eehinatus, 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. 
