270 



STRUCTURE AND LIFE HISTORIES 



(Fig. 185). The cells from this point on, to the forma- 

 tion of the ascus, are diploid, and therefore constitute the 

 sporophytic generation. 



FIG. 195. Lilac mildew (Microsphczra Alni). A, perithecium, with 

 appendages; B, perithecium, showing asci (a); C, an ascus, containing 

 ascospores; D, conidiophore (cph), bearing a chain of conidia (conidio- 

 spores, c.s); E, beginning of fertilization; anth, antheridium; car, carpo- 

 gonium; F, later stage in fertilization; the contents of the antheridium and 

 carpogonium have fused; /, fusion of the two nuclei; G, germination of 

 ascospore (a.s); g.t, germ tube. (E and F after R. A. Harper.) 



226. Germination. When an ascospore germinates it 

 develops directly into a mycelium. 



263. Life-cycle. The life-cycle of Microsphara may 

 be tabulated as follows: 



