FUNGI, WHITE RUST 



259 



Fig. 218. 

 Ripe oospore of Peronospora alsinearum. 



Candida) is very common on the shepherd's purse, deforming the 

 stems, leaves, flowers, and fruit. The mycelium is intercellular, 

 and branched haustoria 

 penetrate the cells. 



419. Asexual stage. 

 The sporophores are short, 

 are developed in great 

 numbers, and crowded un- 

 derneath the epidermis. 

 These sporophores bear 

 chains of spores (conidia; 

 fig. 219), and the mass 

 bursts through the epi- 

 dermis, giving a white 

 rusty appearance. The 

 spores germinate by the 



formation of zoospores as in the grape downy mildew. 



420. Sexual reproduction. This process is very much as 

 described for the downy mildews, but in some species many sperm 



nuclei from the sperm 

 case enter the egg and 

 pair off to fuse with the 

 many nuclei in the egg. 

 431. Formula* for 

 the life history of 

 the water molds and 

 downy mildews. This 

 Fig 2I9> can be written as fol- 



From Cystopus candidus, conidial stage. A, tuft of loWS. Starting with the 

 conidiophores sprus, showing a few conidia in chains; 



B, conidia forming swarm spores or zoospores; C, zoo- fertilized GS.2'. Fertil- 

 spores, some of them germinating; D, germinating zoo- 

 spores, the hyphae about to enter stoma. (After De ized Cfiffif Plant aSCX- 

 Bary.) 



ual spores repeatedly 



formed 



\ 



sperm gamete 

 egg gamete 



fertilized egg, etc., and can be ab- 



* Not to be memorized. Introduced to represent graphically the life 

 cycle. 



