276 



COLLEGE BOTANY 



Albugo occurs on many plants ; among the most conamon is 

 A. Candida (Fig. 126), which attacks members of the Cruci- 

 ferce. The mycelium lives intercellularly in the -host, drawing 

 its nourishment by means of haustoria which penetrate the host 

 cells. Whitish blisters appear under the epidermis of the host, 

 which eventually breaks, liberating great numbers of conidia. 

 These spores are borne in chains., are multinucleate and give rise 



Fig. 125. — Saprolegnia. (a) Infested fly; (6) immature sporangium; (c) mature sporangium: 

 (dj same after the escape of the spores; (e) free-swimming spores. 



to biciliate zoospores. These zoospores swim, for a time, co'me 

 to rest and produce tubes which penetrate and infect seedling 

 plants. The sexual organs are formed on the deep-seated my- 

 celia and on separate hyphse. The oogonium is more or less 

 spherical and multinucleate. The antheridium is multinucleate 

 and produces a small tube which penetrates the oogonium; and 

 discharges its contents. The result of this fertilization process is 



