72 



COMPARATIVE MORPHOLOGY OF FUNGI 



whose much-branched rhizoids are rooted in the substrate and bear on 

 apical lobate processes, numerous thin, generally unbranched, hyphae 

 which usually end with a sporangium (Fig. 41, 1). The zoospores arise, 

 as in the Saprolegnieae, from peripheral protoplasm, shortly before 

 evacuation the inner layer of the sporangial walls swells. The outer 

 cuticular membrane is separated as a small lid at the top of the sporan- 



Fig. 43. — Araiospora -pulchra. Development of oogonia. 1. Young oogonium with 

 peripheral nuclei. 2. Fundament of central egg cell. 3. Mature egg cell whose copulation 

 papilla is in contact with the antheridium. 4. Young oospore with peripheral, faveolate 

 cells. ( X 860; after King, 1904.) 



gium, and the swollen portion forms a tube into which the swarm spores 

 migrate (Fig. 41, 2) and from which they are liberated. This species 

 possesses antheridia and oogonia whose development is still unknown. 



Araiospora is similar in structure and mode of life. It differs from 

 Rhiphidium by the presence of two kinds of sporangia, simple and echinate 

 types (Fig. 42). The latter possess a solid membrane and may pass 

 through a resting period; they are formed under unfavorable growth 

 conditions, such as poor nutrition, low temperature and in places where, 



