CARPOPHTTA. 



175 



The Sac-fungi include 20,000 well-defined species representing 

 six orders, with about 12,000 more whose life-history is so slightly 

 known that they are called the " Imperfect Fungi," and temporarily 

 grouped in three additional orders. 



315. The Simple Sac-fungi (Order 13. Pbrispokia- 

 CEiEs). — These plants, which are mainly parasitic, are com- 

 posed of branching jointed filaments {liyphai) which form 

 a white web-like film upon the surface of the leaves and 

 stems of their hosts. There are both sexual and asexual 

 spores, and of the latter there are in some cases two or 

 three different kinds, which are produced earlier than those 

 that result from a fertilization. 



316. The sexual organs and the spore-fruit resulting 

 from the act of fertilization bear a striking resemblance to 



Fig. 97. 



Fig. 96.— Crrape-mildew (Unoinula). a, a piece of a vegetative hypha, 

 m, m, upon a fragment of the epidermis of the leaf of the grape, and to 

 which it Is fastened by the suckers, U j 6, hypha, with the suckers, ft. seen 

 in side view. Magnified 370 times. 



Fig. 97.— Grass-mildew (Erysiphe communis), cs, vegetative filaments, 

 with a few suckers ; ft, branches bearing conidia ; c, separated conidia. 

 Magnified 135 times. 



those of Ooleochaete, the difference being such as may be 

 accounted for by taking into consideration the aquatic 



