214 



Chlorophycece 



posed of a variable number of cells united by their lateral margins 

 to form a single peripheral layer. In some species the cells are 

 globose, in others more or less angular, and in others they are 

 furnished With projecting processes by means of which they are 

 joined together. The latter forms exhibit intercellular spaces of 

 variable size and the cells are often furnished with a truncate 

 projection (rarely two) on their free outer surfaces. The maximum 

 number of cells observed in a single colony is 64, but in most 

 species the number is 8, 16, or 32. Each cell contains a single 

 chloroplast with one pyrenoid. The multiplication is by typical 

 autocolonies, which are liberated by a split in the wall of the 

 mother-cells or more rarely by the entire gelatinization of the 

 mother-cell-walls. Single spores are sometimes developed from 

 individual cells. 



The two most frequent species are C. sphterwum Nag. (diam. ccenob. 

 1892 p ; diam. cells 423 ^ ; fig. 87 B D) and C. cambric urn Arch. 1868 

 ( = C. pulchrum Schmidle 1892); fig. 87 A. In the former species the cells 

 are somewhat conical with a polygonal base, and in the latter species they are 

 more or less distinctly lobed arid furnished at the same time with a truncate 

 surface projection. C. cubicum Nag., C. microporum Nag., C. verrucosum 

 Eeinsch and C. proboscideum Bohlin are species of considerable rarity. 



Fig. 88. Ccelastrum reticulatum (Dang.) Serm, a small irregular form from 

 Churchill, Donegal, Ireland ( x 475). 



C. reticulatum (Dang.) Senn, which was made the type of the genus 

 Hariotina by Dangeard, differs from all other species in the nature and dis- 

 position of the processes of the cells. The ctenobium consists of 4, 8, or 16 

 cells, and the young autocolonies are retained for a relatively long period 

 within the walls of the mother-cells. The processes of attachment of the cells 

 are narrow prolongations, often curved, and sometimes irregularly disposed. 

 This plant has also been named C. subpulchrum by Lagerheim and C. distans 

 by Turner, but Dangeard's name 1 takes precedence. It is known from 

 Donegal, Ireland 2 , and large colonies are not infrequent in the plankton of 

 Lough Neagh. Diam. cells 6 24 p. ; fig. 88. 



1 Dangeard, 'Memoire sur les Algues,' Le Botaniste, 1889; Chodat & Huber in 

 Bull. Soc. Bot. France, torn, xli, 1894. 



2 West & G. S. West in Journ. Bot. March, 1903. 



