222 



BANGIA. PAET ii. 



shades of green are pretty evenly scattered. The conver- 

 sion of these particles into zoospores has already been 

 described. Since these Algse have no roots, and the cell 

 wall no opening, each cell of a Conferva elaborates inde- 

 pendently the nutriment it absorbs from the water. 

 Some species form a fleecy layer over rocks, and on the 

 bottoms of salt-water pools and estuaries, others extend 

 in bundles in salt-water ditches, and some are found on 

 rocks, between tide marks, rising in long, straight, stiff, 

 and wiry tufts, from three to eight or twelve inches 

 high. 



The genus Hormotrichum, which forms tufts several 

 inches long, of bright grass green, differs from the 

 Confervas in being soft and gelatinous, and even more 

 by its mode of increase, which, however, is still by zoo- 

 spores. The H. collabens may be taken as the type of 

 this genus. It forms a long and large tuft of soft gela- 

 tinous and slippery filaments of glossy green. The joints 

 of the filaments are once, or once and a half, longer 

 than they are broad, and the green granular matter 

 within them is collected into a round sac or sporidium 

 in the centre of each, and after being converted into 

 zoospores, the sac comes through a rupture in the joint 

 into the water, opens, and sets the zoospores free. 



The genus Cladophora, which has twenty-five species 

 in the British seas alone, forms tufts of jointed filaments 

 from four to eight, ten, or even twenty inches high. In 

 some species the filaments are rigid, bristly, and wiry ; 

 in others they are soft and silky ; but they are always 

 richly, variously, and sometimes densely, branched and 

 rebranched. In some the branches and branchlets are 

 forked, in others tripartite ; the Cladophora pellucida, 

 which is a rigid, wiry plant, combines both these forms. 



The genus Bangia consists of purple filamentous 

 jointed and unbranched Algse, which are distinguished 

 from all others by the microscopic arrangement of their 



