446 



PROTOPHVTA 



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. Ban u. d. Leljen d. Oscillarieen, 1845. 

 Braun — Bot. Zeit., 1852, p. 395. 



Bornet and Thuret — Notes Algol., fasc. I, pp. iii. iv. ; and fasc. 2, pp. 1 32- 1 35. 

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



Hansgirg— Oe>terr. Bot. Zeitschr., 1884, pp. 313 et seq. ; and Ber. Deutsch. Bot. 

 Gesell., 1885, p. 14. 



Sub-class 2 and Order 5.— Chroccoccacese. 



The Chroococcace^ 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 (Han sg.), 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 Glceocapsa (Ktz.) it is com- 

 posed of two successive layers, and becomes 

 eventually, in some species, crustaceous, and of 

 a very dark brown or even black colour. The 

 internal pseudocysts or 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). 

 jResti fig- spores or cysts (akinetes) are formed in Glceocapsa 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 



Fig. 374.— Stages in the de- 

 velopment of Chroococcus 

 Uirgidus Nag. (greatly mag- 

 nified). (After Reinke.) 



