170 



FRESH-WATER BIOLOGY 



241 (240) Individual cells flask-shaped, each with a long slender hair from 



the smaller portion Chaetospliaeridiiwi Klebahn. 



Chromatophore 

 parietal, with one 

 pyrenoid. Repro- 

 duction by zoo- 

 spores, four of 

 which are produced 

 in a cell. Horizon- 

 tal divisions of the 

 cells also occurs, 

 the lower of the 

 daughter cells pass- 

 ing gradually to the 

 side of the upper 

 one. 



Chaelosphacridium 

 is widely distrib- 

 uted in the United 

 States though 

 rarely occurring in 

 quantities exceed- 

 ing a few cells at a 

 time. 

 These are usu- 

 ._ ally attached to fil- 

 amentous algae and 

 are inconspicuous, 

 though the long 

 setae are usually 

 somewhat promi- 

 nent 



Fig. 236. Chaetosphaeridium pringsheitnii Klebahn. X about 425. (After Hazen.) 



242 (234) The zoosporangia different from the vegetative cells. 



Subfamily Chroolepideae . . 24^ 



243 (244, 245) Plant minute, tree-like in its branching; reproduction bj 



zoospores Microthamnion Nageli 



Branches from the upper end of a cell and not sepa 

 rated by a membrane; obtuse at the tip; color pale 

 chromatophore a parietal band with no pyrenoid. Zoo- 

 spores formed in zoosporangia at the ends of filaments 



Fig. 237- 



Microthamnion kulzingianum Nageli. 

 (Original.) 



X600. 



244 (243, 245) 



Plant coarse, irregularly branched, partly erect and partl> 

 creeping on stones and trees; when aerial, often colored rec 

 by haematochrome. Membrane thick; reproduction b} 

 zoospores and gametes Trentepohlia Martius 



Chromatophores many, irregular discs, without pyre 

 noids; gameLangia and zoosporangia mostly terminal 

 gametes and zoospores similar, being egg-shaped, wit! 

 two cilia and haematochrome, but no definite pigmen 

 spot. A palmella condition may occur. 



These are sometimes referred to as the aerial algat 

 because they e.xist principally in the air and form oftei 

 bright-colored incrustations on the bark of trees am 

 stones. They are not infrequently found in connectioi 

 with lichen fungi. 



As the Trentepohlias are principally aerial, the lib 

 eration of the zoospores and gametes can occur only a 

 the time of a rain or in the presence of a heavy dew. 



Fig. 238. Trentepohlia wainoi Hariot. X 125. (After 

 Collins and Hariot.) 



