72 Chlorophycece 



and branched, the terminal cells of the branches being rather 

 smaller than the more central cells of the thallus. One or more 

 erect bristles are attached to the dorsal surface of some or all of 

 the cells. These bristles are single, attenuated, and very elongated 

 cells, which have lost their protoplasmic contents and which never 

 possess chloroplasts. They are somewhat fragile and are easily 

 broken off near the base. The sexual organs, which are of very 

 rare occurrence, have been described by Huber 1 , 



The plants occur as epiphytes on species of CEdogonium, 

 Cladophora, Rhizodonium, and Mougeotia, and also on the leaves 

 of Lemna, Elodea, etc. Sometimes well-developed specimens are 

 much branched, the procumbent branches of the Alga often 

 following the contours of the cells of the plant to which it is 

 attached, and in consequence exhibiting a marked reticular 

 structure 2 (fig. 19 B). The cells contain a single parietal chloro- 

 plast with one (or more ?) pyrenoids. 



There has been much confusion with regard to the two names 

 Aphanochcete and Herposteiron. The arrangement proposed by 

 .Hansgirg, and subsequently adopted by De Toni, Wille and others 

 (myself included), of two distinct genera is quite untenable. There 

 can be no doubt in the mind of anyone who has studied these 

 plants carefully that Herposteiron confervicola Nag. and Aphano- 

 chcete repens A. Br. are descriptions of the same plant, and this is 

 amply confirmed by the authentic drawings by Nageli published 

 by Huber. Both Huber and Klebahn admit the identity of 

 Herposteiron and Aphanochcete, but reject Nageli's name on the 

 ground of the incompleteness of the description. There is, however, 

 far more reason for neglecting Braun's name on the ground of 

 inaccuracy. 



H. confervicola Nag. ( = Aphanochcete repens A. Br.) is a species with 

 oblong-ellipsoidal cells, each bearing a single bristle which is little swollen at 

 the base and which is attached towards one end of the cell. It is not an un- 

 common species and is somewhat variable, two bristles being frequently 

 attached to some of the cells of the thallus. (Figs. 18 and 19 B D.) Another 

 species, H. pilosissima (Schmidle) nob. ( = Aphanochcete pilosissima Schinidle), 

 is more abundant in some parts of the British Islands and is most probably 

 identical with H. polychcete Hansg. The cells are more ellipsoidal and possess 

 from one to four bristles, each bristle having a swollen base (fig. 19 A). 



1 Huber in Bull, de la Soc. hot. de France, xli, 1892. 



2 G. S. West in Journ. Bot. Febr. 1899, p. 57. 



