244 



THE FUNGI 



The suppression of a sexual act is termed by botanists apog- 

 amy (meaning without marriage), or sometimes parthenogenesis, 

 when the egg itself develops without fertilization. Apogamy is 

 found in many groups of plants,- - in the algre and fungi, among 

 the ferns, and even in the seed plants. 



FIG. 214. A water mold (Saprolegnia mixta) 



A, habit sketch of the mycelium around a fly ; sporangia being formed at the tips 

 of the longest hyphje and sexual organs nearer the body of the insect ; 1> , tip 

 of hypha ; C, terminal sporangium rilled with zoospores ; I), empty sporangium 

 with a group of zoospores near the opening; E, empty sporangium with the 

 hypha continuing its growth inside; F, an oogonium containing many eggs 

 and with three antheridial filaments applied to it 



263. The blights. The blights (order Peronosporales) are 

 parasitic fungi which cause some very destructive plant diseases. 

 Some of them are also called " downy mildews," but it would be 

 better if the term mildew were reserved for a peculiar group of 

 sac fungi (Sec. 266). The hyphae form extensive growths in the 

 tissues of the hosts. The asexual fructifications appear on the 

 surface, but the sexually formed oospores are developed within 



