CH. X] 



THE ALGAL FUNGI 



435 



spores, either free-swimming or wind-carried, according to 

 habit, and in part sexually by methods almost identical with 

 those in Green Algae. They fall into three principal orders 

 as follows : 



SAPROLEGNIALES : THE WATER MOLDS. 

 PERONOSPORALES: THE BLIGHTS OR DOWNY MIL- 



ORDER 1. 

 ORDER 2. 



DEWS. 

 ORDER 3. 



MUCORALES: THE TRUE MOLDS OR BLACK MOLDS. 



ORDER 1. SAPROLEGNIALES (OOMYCETES IN PART): THE 

 WATER MOLDS. These live on the floating bodies of dead 

 insects, tadpoles, and small 

 fish, where they appear as 

 a woolly wrapping of white 

 hyphsB, while they also 

 attack small living fish, 

 through the gills, often 

 causing great losses in fish 

 hatcheries. In the common 

 and typical Saprolegnia 

 (Fig. 302), the plant body 

 suggests a mass of colorless 

 Vaucheria threads, com- 

 posed of multinucleate cce- 



nocytes, sending haustoria 

 into the substratum or host. 

 Asexual reproduction 



oc- 





FIG. 302. Saprolegnia species. As 

 it appears ordinarily on a dead insect in 

 water, natural size, and portions, X 200. 



i , . .,. , Left, the crenocytic hyphae bearing 



CUrS through blClliate ZOO- oogonia, with fertilization of the egg cells, 

 Spores formed in elongated in various stages ; and right, formation 

 T of zoopores. (Chiefly from Kerner.) 



sporangia. In sexual re- 

 production (when present, as it often is not), lateral oogonia 

 are formed in which are usually several egg cells ; tubular 

 antheridia grow towards and into contact with these oogonia, 

 into which they send tubes carrying each a sperm nucleus to an 

 egg cell, a method curiously anticipatory of that used in the 

 fertilization of the egg cell by the sperm nucleus in the pollen 

 tube of the higher plants. The resultant oospores acquire 



