20 Transactions British Mycological Society. 



cells, this tendency to hypha-like proliferation in response to 

 a peculiar environment is of common occurrence, as for example 

 in cartilage tissues grown aseptically under artificial conditions. 

 As regards the latter, the parallel is so close to the growth of 

 a fungus mycelium that a friend who was investigating the 

 growth of animal tissues under cultural conditions, at first 

 thought that his cultures had become contaminated by a fungus ; 

 the hypha-like threads were in fact nothing but proliferating 

 cartilage cells. Thus the mycelial character of the vegetative 

 body of most fungi must be looked upon as a type of cell 

 development elaborated in connection with special nutritive 

 needs, and not in any way as being mainly the expression of an 

 algal ancestry. 



Another marked difference between the fungi and the algae, 

 and indeed all other groups of green plants, lies in the chemical 

 composition of the cell membranes. It has long been known 

 that the cell walls of fungi differ chemically from the cellulose 

 which is the chief constituent of the cell walls of other plants. 

 At first the main constituent of hyphal walls was called " fungus- 

 cellulose," but more recently it has been shown that this 

 substance contains nitrogen whereas true cellulose does not, so 

 that it differs markedly. The main constituent of fungal walls 

 resembles in many ways the chitin of animal cells. Recent 

 investigations tend to emphasise the phylogenetic significance 

 of the chemical constitution of cell membranes, and it seems 

 clear that if the fungi had been derived from the algae there 

 would be closer approximation in the characters of the mem- 

 branes. For instance, the chemical differences between the cell 

 walls of Pythium and Vaucheria make it certain that an immense 

 gap lies between them, apart from all other considerations. 

 While mentioning chemical differences between fungi and other 

 plants, it may be pointed out that many fungus pigments are 

 highly peculiar, especially those of the lichens. On the other 

 hand most of the pigments of green plants show close relation- 

 ships to one another. 



With these profound and fundamental differences between 

 the fungi and the algae it may not be unprofitable to consider 

 in some detail the view which has been put forward by Dan- 

 geard* and others that the origin of the fungi is to be sought 

 in unicellular protist organisms. Dangeard has had a unique 

 experience as an investigator of the lower forms of life, both 

 plant and animal, and his views are entitled to most serious 

 consideration. In the main I am in harmony with him although 

 I cannot agree with some of his deductions. At the bottom 



* Dangeard, P. A., Les ancetres des champignons superieurs. Le Botaniste, 

 IX, p. 157 (1903)- 



