278 



PART IV. — VEGETABLE TAXONOMY. 



pal groups, the Micrococcus or spherical forms, the Bacterium 

 or rod-like forms, the Bacillus or filiform forms, and the Spirillum 

 or coiled forms. In the Micrococcus genus the cells are exceed- 

 ingly minute, rounded and either distinct or united loosely like a 

 string of beads. In the genus Bacterium, the cells are also inde- 

 pendent or very loosely united and cylindrical in shape with 

 rounded ends, which sometimes, at least, are provided with cilia. 

 Under the Bacillus- a bed 



group several genera 

 are distinguished ac- 

 cording to the shape 

 of the filaments. The , 

 Bacillus proper con- 

 sists of short, straight 

 but slender filaments ; 

 the genus Leptothrix 

 have the filaments slen- 

 der and long ; in the ,• 



genUS Beggiatoa the Fig. 468. — Forms of Bacteria, a, Micrococcus, mag- 



' . nified about 1,800 diameters; b, Bacterium termo, magni- 



filamentS are thicker fied about 1,500 diameters ; c, Bacillus tuberculosis, 



, . , magnified about 1,800 diameters ; d, Leptothrix buccalis, 



and long ; in the genUS magnified about 800 diameters; e, Beggiatoa alba, mag- 



r^l J tl, ' fV> fil nified about 600 diameters; f, Cladothrix dichotoma, 



daQOtnriX tne nla- magnified about 1,000 diameters ; £■, Crenothrix Kfihniana, 



f K n V>* • magnified about 300 diameters; A, Spirillum undulu, 



mentS are Drancning ; magnified about 800 diameters; i, Spirochete plicatilis, 



and in the genus Cren- ma s nified about *» diameters, 

 othrix they are simple but enclosed in a gelatinous or mucilagin- 

 ous envelope. In the Spirillum group, the genus Spirillum con- 

 sists of filaments which have but few coils, but the coils are 

 rigid ; in the genus Spirochaete the filaments are slender, many- 

 coiled and not rigid. 



Some idea of the more prominent types may be obtained 

 from the illustrations, Fig. 468. 



THE CYANOPHYCEjE. 



The term is derived from two Greek words, which literally 

 mean " blue-green sea-weed." The plants are mostly inhabitants 

 of fresh water, though a few are marine, and they contain, in 

 addition to chlorophyll, a blue, and also sometimes brownish or 

 reddish, coloring matters in their cells. In some species the cells 

 are distinct; in others they are more or less united into chains 



