140 



RESEARCHES ON FUNGI 



The Algae. — In the Algae, various degrees of co-operation 

 between individuals of the same species are exhibited. Among 

 the Cyanophyceae, the Chlorophyceae, and the Phaeophyceae there 

 are numerous species in which many individual plants live together 

 in the same mass of jelly on an equal basis (Figs. 74 and 75). The 

 communal organisation in these colonies is of the lowest possible 



Fig. 72. Two large Douglas Fir trees {Pseudotsuga taxijolia) united together by the 



natural graftage of lateral roots. The united roots, which protrude above the 

 forest floor, are well seen in the centre of the photograph. Photograph by C. A. 

 Pemberton, taken in British Colmiibia, Canada. 



type. A slight advance on this (Fig. 76) is to be found in 

 such branched colonial forms as Dinobryon (Phaeophyceae), 

 Gomphonema (Chrysophyceae), and Licmophora (Bacillariales). 

 In Hydrodictyon, the Water-net, a large number of zoospores 

 arrange themselves to form a non-motile coenobium of coenocytes, 

 a curiously reticulated structure in which all the coenocytes 

 have equal value so far as reproduction is concerned (Figs. 77 

 and 78). 



In the Volvocaceae, as is well known, there is a series of algae— 

 usually regarded as colonial — whose highest forms, in the structure 

 and functions of the cells of which they are composed, clearly 



