THE FUNGI : ARCHIMYCETES AND PHYCOMYCETES 237 



sporangia. It is interesting to note that during the development of the 

 sporangia they are protected by the host epidermis, which is only ruptured 

 when at last the distal sporangia are mature. 



Fig. 228. — Cystopus candidiis. Section through stem of 

 host showing sporangiophores and abstricted zoo- 

 sporangia covered by the remains of the epidermis. 



The zoosporangia are finally liberated and disseminated by the wind, 

 and when conditions are favourable, that is, when the atmosphere is damp, 

 they germinate by producing a number of zoospores (Fig. 229) in each 

 zoosporangium. These zoospores are kidney-shaped with two laterally 

 placed flagella. From these zoospores fresh infections of host plants are 

 derived. 



It is sometimes stated that Cystopus reproduces asexually by means of 

 conidiospores. According to this view the sporangiophore is regarded as a 

 conidiophore, from the tip of which conidiospores are abstricted in acropetal 

 succession, in a way similar to that found in many Fungi, e.g, Aspergillus. 

 It is certainly true that the method of abstriction of the zoosporangia in 

 Cystopus is effected in much the same way. The difference lies in the method 

 of germination of these zoosporangia. The typical conidiospore germinates 

 by means of a germ tube and thus forms a hypha directly, one hypha being 

 normally formed by each conidiospore. In Cystopus, as we have seen, the 

 zoosporangium gives rise on germination to a number of zoospores, which 

 are not only actively motile but capable of affecting a separate infection of 

 the host tissue. It follows that the structure producing these zoospores must 

 be regarded as a zoosporangium, comparable with that oi Pythiiim. 



From this we may conclude that the typical conidiospore is equivalent to a 



