214 



MORPHOLOG Y. 



these views, might be presented here to show the general relationships of 

 the fungi studied, with the addition of a few more in orders not represented 

 above. It should be borne in mind that the author in presenting this view 

 of classification does not necessarily commit himself to it. It is based 

 on that presented in Engler & Prantl's Pflanzenfamilien. There are three 

 classes. 



I. Class Phycomycetes (Alga- like Fungi). 



1. SUBCLASS OOMYCETES. 



432. These are the egg-spore fungi. They include the water mold 

 (Saprolegnia), the downy mildew of the grape (Plasmopara), the potato 



\d 



Fig. 249. 



Chytrids. A, Harpochytrium hedenii, parasitic on spirogyra threads; a, sickle- 

 form plant; b, the sporangium part with escaping zoospores; c, old plant pro- 

 liferating by forming new sporangium in the old empty one; d, zoospore; e, two 

 young plants just beginning to grow. B, Rhizophidium globosum parasitic on 

 spirogyra. Globose sporangium with delicate threads inside of the host, zoospores 

 escaping from one. C, Olpidium pendulum, parasitic in spirogyra cell. Ellip- 

 tical sporangium with slender exit tube through which zoospores are escaping. 

 D, Lagenidium rabenhorstii parasitic in spirogyra cell. Two slender sporangia 

 with exit tubes through which protoplasm escapes forming a rounded mass at the 

 end of tube, this protoplasm forming biciliate zoospores. 



forming swarm spores which unite to form a small plasmodium, which in 

 turn grows to form a large plasmodium or protoplasmic mass. It is doubt- 

 ful if they are any more plant than animal organisms. Examples: Trichia, 

 Arcyria, Stemonitis, Physarum, Ceratiomyxa, etc., on rotten wood; Plas- 

 modiophora brassicae is a parasite causing club foot of cabbage, radishes, 

 etc. It lives within the roots, causing large knots and swellings on the same. 



