216 



BOTANY. 



phycocyanine and a less soluble onephycoxanthine.* 

 Structurally the members of this class differ but little from 

 the Schizomycetes, although they are of a much larger size. 

 The cells generally show a little more coherence than in the 

 last class. 



They live in fresh or stagnant water, or upon damp 

 ground, rocks, or decaying wood. Unlike the Schizomycetes, 

 they do not normally inhabit putrid solutions. 



282. Order Chroococcacese. This is made up of uni- 

 cellular plants. The cells, which are spherical, oblong, cylin- 

 drical, or angular, are either single, or more commonly united 

 by a common jelly into families. Cell-division (in reality 

 internal cell-division) takes place in 

 either one, two, or three planes (Fig. 

 147). 



Thirteen genera are known in the United 

 States : (1) Chroococcus, with globose, oval, 

 or angular (from pressure) cells, which are 

 solitary or in free families; our four species 

 grow on wet rocks or in springs; (2) 

 Glceocapsa (Fig. 147), with spherical cells, 

 which are solitary or in enclosed families ; 

 Fig. Ut.-Glasocapsa in dif- our eleven species form a firm grumous or 



gelatinous coating of a light brown color 



r n , . 



on wet rocks ; (o) UlCBOSp/icenum, with very 



small cells, forming a thallus-like mass; we 

 have one species, forming a light-colored 

 gcum on stagnant water . ( 4 ) Merismopedia, 



with globose, oval, or oblong cells, which occur in tabular families of 

 four, eight, sixteen, etc. ; our two species inhabit streams and fresh 

 ponds. Claihrocystis, Anacystis, etc., are common. 



283. Order Nostocaceae. The plants of this order are 



* Phycocyanine, the blue coloring-matter, is extracted from the 

 crushed plants by cold water ; the solution is blue by transmitted and 

 blood-red by reflected light. After the extraction of phycocyanine, 

 treatment of the crushed plants with strong alcohol produces a green 

 solution which contains chlorophyll, and a yellow coloring-matter, 

 phycoxanthine ; the latter maybe separated by shaking up with the 

 green solution a large quantity of benzine, which takes up the chloro- 

 phyll, and when at rest rises and forms a green upper layer containing 

 chlorophyll, below which is the yellow alcoholic solution of phycoxan- 

 thine. 



. . 



ferent stages of growth, show- 

 ing mode of cell-multiplica- 

 tion. The daughter cells are 



youngest ; E, oldest stage 

 x aoo.-After Sachs. 



