113 



BOTANY. 



Class in. Geeen Slimes {Gyanophyceoe). 



229. These are single cells, or chains of cells, usually of 

 a blue-green or hrowiiish-green color, and generally inhab- 

 iting the water. They very commonly form slimy masses 

 or films on the water, or the moist surfaces where they 

 grow. In their decay they emit a putrid odor, and when 

 abundant, as they sometimes are in city water-supplies, are 

 quite troublesome and offensive. 



230. The lower Green Slimes are single-celled, as in 



B^a.48. 



I^s. 49. 



Fig. 48.— Cells of QloBOoapaa in different stages of growth, showing division 

 and the mode in which the daughter-cells are -surrounded and enclosed by the 

 gelatinous walls of the mother-cells, ^.youngest; .E, oldest stage. Magnified 



Fio. 49.—^, filament of Nostoc; B, end of filament of Osoillaria. Magnified 

 300 tunes. 



Chroococcus, Gloeocapsa (Fig. 48), and other genera. Each 

 cell divides into two, and these soon divide again, and so 

 on. In Gloeocapsa the cell-wall is much swollen into a 

 jelly-like mass. 



231. In the Nostocs and their near relatives (Osoillaria) 

 there is a little coherence of the cells into chains or fila- 

 ments. The cells form by fission, but after formation 

 adhere somewhat to each other. The Nostocs (Fig. 49, A) 

 occur in water or on moist ground as Jelly-like masses of 



