286 



GENERAL MORPHOLOGY OF PLANTS 



434. Formula* for the life history of the water molds and 

 downy mildews. This can be written as follows, starting with 

 the fertilized egg: Fertilized egg Plant asexual spores re- 



/sperm gameteX p 



peatedly formed < Mertilized egg, etc., andean 



\egg gamete / 



be abbreviated as follows: FE P asp P asp P 





FE, 



etc. In some of the blights and downy mildews zoospores are 



Fig. 230. 



From Cystopus candidus, conidial stage. A, tuft of conidiophores from sorus, showing a 

 few conidia in chains; B, conidia forming swarm spores or zoospores; C, zoospores, some of 

 them germinating; D, germinating zoospores, the hyphae about to enter stoma. (After De 

 Bary.) 



produced on the germination of the fertilized egg. The formula 

 for these could be written as follows: FE sp P asp P 



asp P/ 5 /FE, etc. If g is allowed to stand for each of the 

 gametes, the formula could be written as follows: FE sp P 



asp P \ ^ /FE, etc. Various methods can be devised to 



X g/ 

 represent the life history. 



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



