1885.] 



MICROSCOPICAL JOURNAL. 



The desmids and diatoms are not re- 

 garded in this classification, the former 

 having been adequately treated by Mr. 

 Wolle, and the diatoms by various 

 authors. 



The colored protoplasm of the cells 

 of algai is known as the endochrome. 

 The color is due to chlorophyll, 

 which may be either pure (green), 

 or mixed with other coloring matters 

 such as a blue (phycocyanin), a red 

 phycoerythrin), a brown (phycophse- 

 rin), which impart to it various shades 

 of color. The colors afford a means 

 of distinguishing several classes which 

 have received corresponding names, 

 thus we have — 



1. Chlorospermea^, Harvey ; Chlo- 

 rosporete, Thuret ; Chloro phyllo- 

 phvceiE, Rabenhorst. Green, chlo- 

 rophyllous algae. 



2. CyanophvcecE, Sachs ; Phyco- 

 chromacejE, Cohn ; Phycochromo- 

 phyceae, Rabenhorst. Bluish-green 

 algae. 



3. Melanospermete, Harvey; Me- 

 lanophyceae, Rabenhorst; Phaeospo- 

 reae. Thuret. Olive-green, brown or 

 blackish algie. 



4. Rhodospermeae, Harvey ; Rho- 

 dophvccce, Rabenhorst. Red algae. 

 ■ By far the greater number of algae 

 found in fresh water belong to the 

 first two classes, a few belong to the 

 third. All the red algje are marine. 



The separation of the algae into 

 classes founded upon the coloring 

 matter within their cells is too purely 

 artificial to form basis of a scientific 

 classification. We have only par- 

 tially adhered to it in this place, 

 and that merely as a matter of 

 convenience ; but it separates many 

 species that are unquestionably closely 

 related, and which should be placed 

 in the same genera. Thus, there is 

 not the slightest doubt that various 

 forms of unicellular algae such as 



Gloeocapsa and Glceocystis, for ex- 

 ample, are genetically connected, yet 

 some are green and others are olive- 

 green. 



• Many of the divisions of families 

 and descriptions of genera are taken 



largely from Kirchner's work, al- 

 though the arrangement is not entirely 

 the same, and Rabenhorst's and other 

 works have been carefully studied in 

 the same connection. 



The descriptions are limited to the 

 genera, since it would enlarge this 

 work too much to include descrip- 

 tions of species. 



The writer would be very glad to 

 receive suggestions from persons us- 

 ing this key, which will enable him 

 to improve upon it in future ; and he 

 would be especially grateful for cor- 

 rections of errors that may be found 

 in it. 



I. ORDER PROTOCOCCOIDE/E Kirch. 



Unicellular algae, of chlorophyll- 

 green color, propagating by swarm- 

 cells. Without terminal growth, not 

 branching. 



The thallus of these algcE consists 

 during their entire life either of a sin- 

 gle cell, or else the single cells remain 

 united in a more or less close paren- 

 chymatous-like combination, still in- 

 dicating in this case their unicellular 

 character since in each of the cells 

 all vegetative and reproductive pro- 

 cesses take place. 



Propagation either sexual, by 

 oogonia and antheridia, or by copula- 

 tion of swarm-spores. 



Cell - contents chlorophyll - green 

 (very rarely reddish yellow or brown), 

 never bluish green. 



FAMILIES. 



Propagation by swarm-spores, and 

 cell-division. . The single cells either 

 free or united by a gelatinous matrix, 

 stems, etc. Copulation of swai^m- 

 spores not observed. 



Palmellacce^e, I. 



Vegetative cells not ciliated, either, 

 single or in coenobia. Propagation 

 by copulation of swarm-cells and by 

 asexual zoospores. No vegetative 

 cell division. Protococcacc^, II. 



Vegetative cells during their entire 

 life motile. Reproduction sexual, 

 or asexual by copulation of swarm- 

 cells, Volvocace^, in. 



