274 



PLANT STUDIES 



(lew, llIicrnsjiJKPra, grows on lilac leaves, which nearly al- 

 ways sliow the whitish covering after maturity (Fig. :^41). 

 The branching hyphaa show numerous 2)artition walls, and 

 are not cosnocytic as in the Phycomycetes. .Small disk-like 

 haustoria penetrate into the supci'ficial cells of the host, 

 anchoring the mycelium and al>sorl)ing the cell contents. 



SporojDhores arise, whicii form asexiial sjoores in a jie- 

 culiar way. The end of tlie S2)oro])hore roumls off, almost 

 separating itself from the part below, and Ijecomes a spore 

 or spore-like body. Below this another organizes in tlie 



same way, then another, until 

 a chain of spores is developed, 

 easily broken apart and scat- 

 tered by the wind. Falling 

 upon otlier suitalile leaves, 

 tliey germinate and form new 

 mycelia, enabling the fungus 

 to spread rapidly. This metli- 

 od of cutting a branch into 

 sections to foi'ui K23oi'es is 

 called (il)sfrirti(iii, arid tlie 

 spores formed in this way 

 are called cdiiidia, or conidi- 

 ospores (Fig. 243, B). 



At cei'tain times the myce- 

 lium develops special liranclies 

 which develop sex organs, liut 

 they are seldom seen and may 

 not always occur. An oogo- 

 uiuni and an aiitheridium, of 

 scii'carps.- file usual fomis, but probably 

 witliout organizing gametes, 

 come into contact, and as a 

 result an elaborates structure is developed — the ascorarp, 

 sometimes called the "spore fruit." These ascocarjis aji- 

 pear on the lilac leaves as minute dark dots, each one beino- 



