THE BLUE-GKEEN ALG.E 



25 



the famous eruption of Krakatoa, whose streaming lavas 

 destroyed all vestiges of life in the area over which they 

 poured, the first plants to colonize 

 the lifeless lava- waste were Blue- 

 Green Algse. They have been lff(ffi ^ N 

 recognized as the first plant 

 colonists of fresh lavas in other 

 places. In 1874 a species (Der- 

 moglcea Limi) appeared in the sea 

 off the Adriatic coasts, and multi- FIG. 9. GLOSOCAPSA POLY- 



plied so extensively that the fishing DERMATICA ( STXASS- 

 . , -11 BURGER). HIGHLY MAG- 



industry was seriously hampered, NmED . 



but after six Weeks the nuisance A, Beginning to divide ; 



suddenly dis- B > shortl y after division ; 

 % C, a later stage. 



appeared. 



The simplest Blue-Green Algae are 

 included in the family Chroococ- 

 cacese ; they are all one-cell forms 

 which have the habit of cohering 

 in colonies. One genus, Gloeocapsa 

 (Fig. 9), establishes itself in small 

 gelatinous colonies on damp walls 



and rocks, and not infrequently on 

 FIG. 10. NOSTOC , , , . , ax 



LINCKII. x 470. hot-house window-panes. Stagnant 



A, Portion of a filament; water is frequently covered with 

 h, h, hetero-cysts; sp., films of Merismopedia. The method 



sp., spores; B, germin- ,. , . ,. . A t . , * i 



ating spore ; <?, young of multiplication is that of simple 



filament from spore ; fission. 



ruptured cell- wall of T TVT /TO- i A\ i 



spore seen at ends. , In Nost G ( Fl g- 10 ) We nave a 



filamentous form. It occurs com- 

 monly in round, bluish - green, jelly-like masses on 

 damp soil, in farmyards, on walls and garden walks. 



