Pleurococcacece 



205 



cells. The cells are of a variable shape and the branches are 

 sometimes a little at- 

 tenuated. There is a 

 large parietal chloro- 

 plast in each cell con- 

 taining a single pyre- 

 noid. 



P. viride Kiitz. (fig. 83 

 A C) is usually found 

 epiphytic on larger Algae, 

 such as Coleochcete orbicu- 

 laris, or on the stems and 

 leaves of aquatic Phanero- 

 gams, such as Callitriche, 

 JElodea, etc. I have pre- 

 viously suggested 1 that 

 certain plants described 

 as Entocladia gracilis 

 Hansgirg 2 ( = Endoderma 

 gracile De Toni) are most 

 probably referable to Pro- 

 toderma viride Kiitz. 



Fig. 83. A -C, Protoderma viride Kiitz., from 

 Baildon, W. Yorks. , epiphytic on Callitriche stag- 

 nalis; AandB, outlines of colonies, x 520; C, single 

 cell, x 700. D, Hormotila mucigena Borzi, from 

 Boston Spa, W. Yorks. (x520). 



Genus Hormotila 

 Borzi, 1883. The vege- 

 tative cells are spheri- 

 cal, ovoid, or ellipsoid, rarely oblong, and from two to sixteen 

 of them occur within a more or less ample, firm, gelatinous in- 

 tegument, which is often concentrically lamellose. There is a 

 large chloroplast in each cell, frequently very granulose and destitute 

 of a pyrenoid. Multiplication takes place by cell-division, at first 

 in three directions, but subsequently in two, and finally in one 

 direction. In this way more or less moniliform series of cells are 

 produced, all of which are connected by cylindrical lamellose 

 integuments. Zoogonidangia arise from vegetative cells by an 

 increase in size of the cell, and reproduction takes place by 

 numerous minute zoogonidia, each with two cilia. Gametes have 

 not been observed. 



The only known species is H. mucigena Borzi, an Alga which I have 

 observed from Boston Spa in West Yorkshire. It forms an expanded, dull 



1 G. S. West in Journ. Bot. Febr. 1899, p. 58. 



2 Hansgirg, ' Ueber Entocladia Reinke und Pilinia Kiitz.,' Flora, 1888, no. 33, 

 t. xii, f. 615. 



