194 FRESH-WATER ALG^E OF THE UNITED STATES. 



PALMELLA BOTRYOIDES, Kg., including P. heterospora, Bab. 



Thallus gelatinous, spreading, soft or firm, somewhat 

 tubercular, green or yellowish. Cells mostly spherical and 

 often very unequal in size ; membrane of cells thin, contents 

 chlorophylous green. 



Diameter of cells, 2-4 yu. 



On old wet wood ; frequent after a rainy season. 

 Plate CLXII, fig. 8, section of a thallus. 



^ 



Genus 57, PORPHYEIDIUM, Naeg. 



The diagnosis which hitherto obtained for this genus, reads : 

 Thallus between gelatinous and membranaceous, somewhat in- 

 crusting, long and broadly expanded, composed of globose or 

 many-sided cells. 



PORPHYRIDIUM CRUENTUM, Naeg. 



Thallus spreading, gelatinous, composed of a single layer 

 of cells, sometimes two or more ; lighter or darker red, cells 

 normally globose, but when crowded, angular. 



This is another vague genus ; has only one species and 

 that, relying upon personal observations upon many speci- 

 mens, is identical with Protococcus miniatus. The cells are 

 the same in size ; color of the one as of the other is change- 

 able, first green then orange or red ; habitats are also the 

 same ; the one more frequent on the flower pots, or walls of 

 conservatories, and the other on the ground floors, but 

 neither are confined to these localities ; they occur on wet 

 or shaded grounds, pavements, etc.; on a sultry summer's 

 day side- walks are sometimes blotched with red as with 

 blood stains ; on examination these are found to be com- 

 posed of an almost infinite number of small spherical cel- 

 lules, rarely with the sides compressed, or angular. 



Syn. Palmella cruenta, Ag. ; Tremella cruenta, Eng. Bot. Com- 

 pare Protococcus miniatus, page 181. 



Plate CLXVI, fig. 1, a very small portion of thallus, which 

 often extends for feet over moist earth ; younger portion 

 green and older parts lighter or darker red. Seen under 

 low magnifying power. 



Genus 58, BOTEYDINA, Breb. 



Cells spherical or oblong, involved in a very thick, gelatinous, 

 partially diffluent integument, in large families, which are often 

 numerous, enclosed in a mother cell which constitutes a subglo- 

 bose thallus. 



