446 



PROTOPHYTA 



organism with blue-green endochrome which he regards as the swarm- 

 cell condition of a phycochromaceous alga which occurs normally in a 

 filamentous form, probably as Oscillaria tenuis (Ag.) or O. Frolichii 



(Ktz.). 



Literature. 



Fresenius — Ueb. d. Bau u. d. Leben d. Oscillarieen, 1845. 

 Braun— Bot. Zeit., 1852, p. 395. 



Bornet and Thuret — Notes Algol., fasc. I, pp. iii.-iv. ; and fasc. 2, pp. 132-135. 

 Zukal — Oesterr. Bot. Zeitschr., 1880, p. 11. 



Hansgirg— Oesterr. Bot. Zeitschr., 1884, pp. 313 et seq. ; and Ber. Deutsch. Bot. 

 Gesell., 1885, p. 14. 



Sub-class 2 and Order 5. — Chroococcaceae. 



The Chroococcaceae share with the Schizomycetes the distinction 

 of being among the lowest forms of vegetable life. The separate 

 cells are always microscopic, and are filled with a blue-green or violet 

 endochrome which owes its colour to the phycocyanin dissolved in the 

 cell-sap ; they contain neither distinct chlorophyll-grains nor starch, nor, 

 except in Chroodactylon (Hansg.), a distinct nucleus. The cells are either 

 isolated, or are more often connected together 

 into colonies by a mucus formed from the 

 disintegration of the outer layers of the cell- 

 wall ; they are never united into a filament. 

 This gelatinous envelope is either colourless and 

 hyaline, or of a blue, brown, or olive colour, 

 and is often strongly lamellated. In Chroo- 

 coccus (Nag.) it is homogeneous and capable of 

 swelling greatly; in Gloeocapsa (Ktz.) it is com- 

 posed of two successive layers, and becomes 

 Fig -Sta es in the de eventually, in some species, crustaceous, and of 

 veiopment of chroococcus a vcry dark brown or even black colour. The 



tu-rgldus Nag. (greatly mag- • ^ 1 , , . • j , , 



nified). (After Reinke.) mtemal pscudocysts OX gonids are never endowed 



with cilia, as in some Protococcaceae, and are 

 usually quiescent ; but in Microcystis (Ktz.) they have a constant 

 ' swarming ' motion within the hyaline envelope. The entire organism 

 has usually a power of slow spontaneous motion. Multiplication by 

 swarm-spores or zoospores is unknown except in the doubtful case 

 of Merismopedia (Mey.) (Goebel, ' Outlines of Classification,' p. 22). 

 Resting-spores or cysts (akinetes) are formed in Gloeocapsa by the 

 cells of which a colony is composed investing themselves, while still 

 within their common gelatinous envelope, in a rough or spiny coat of 



