THALLOPHYTES : FUNGI 51 



One of the ordinary life processes which seems to be 

 seriously interfered with by the saprophytic and parasitic 

 habit is the sexual process. At least, while sex organs 

 and sexual spores are about as evident in Phycomycetes 

 as in Algae, they are either obscure or wanting in the 

 Mycomycete groups. 



1. Phycomycetes (Alga-Fungi) 



39. Saprolegnia, — This is a group of " w ater-m oulds," 

 with aquatic habit like the Algae. They live upon the dead 

 bodies of water plants and animals (Fig. 33), and some- 

 times attack living fish, one kind being very destructive 

 to young fish in hatcheries. The hyphae composing the 

 mycelium are ccenocytes, as in the Siphon forms. 



Sporangia are organized at the ends of branches by 

 forming a partition wall separating the cavity of the tip 

 from the general cavity (Fig. 33, B). The tip becomes 

 more or less swollen, and within it are formed numerous 

 biciliate zoospores, which are discharged into the water 

 (Fig. 33, C), swim about for a short time, and rapidly form 

 new mycelia. The process is very suggestive of Cladophora 

 and Yaucheria. Oogonia and antheridia are also formed 

 at the ends of the branches (Fig. 33, F), much as in Yau- 

 eheria. The oogonia are spherical, and form one and some- 

 times many eggs (Fig. 33, D, E). The antheridia are 

 formed on branches near the oogonia. An antheridium 

 comes in contact with an oogonium, and sends out a deli- 

 cate tube which pierces the oogonium wall (Fig. 33, F). 

 Through this tube the contents of the antheridium pass, 

 fuse with the egg, and a heavy-walled oospore or resting 

 spore is the result. 



It is an interesting fact that sometimes the contents of 

 an antheridium do not enter an oogonium, or antheridia 

 may not even be formed, and still the egg, without fertiliza- 

 tion, forms an oospore which can germinate. This peculiar 



