454 A TEXTBOOK OF BOTANY [Ch. X 



secretes a sweet liquid, honey dew, which attracts insects, 

 by whose movements the spores are transferred to other 

 Rye flowers; and herein we have perhaps the first case in 

 the ascending scale where insects are utilized by plants. 

 Ultimately the mycelium absorbs all of the contents of the 

 ovary, which it fills with its own compact, dark purple my- 

 celium, or sclerotium. This dark purple, sclerotized ovary, 

 which projects from among the uninjured grains in the head 

 of Rye, is used in medicine, under the name of ergot, on 

 account of its astringent power of contracting muscles. 

 These sclerotized grains fall to the ground and live over win- 

 ter. In spring they develop stalked, globular, rose-colored 

 heads, in which are buried many perithecia. Therein are 

 produced the ascospores, which are carried by the wind to 

 other developing Rye plants. 



To this group belongs also the very destructive Chestnut 

 disease (Endothia parasitica), introduced a few years ago 

 from eastern Asia, and now working sad havoc among 

 American Chestnut trees. The spores are carried by wind, 

 and incidentally by birds and insects. Reaching the bark 

 of a Chestnut, they develop mycelia which penetrate to the 

 phloem and cambium, and encircle the stem; and this is 

 soon killed. Later the dead bark becomes warty, with 

 yellowish-brown pustules developing through the lenticels; 

 in these are formed great numbers of summer spores, 

 which are extruded in twisted threads, and infect other 

 trees. In autumn, the same pustules develop buried peri- 

 thecia with ascospores (winter spores), also wind-carried. 

 These germinate the next spring, when the old mycelium also 

 renews its growth, and continues to destroy the tree down- 

 ward. No method has been found for killing the deeply buried 

 mycelium or checking the formation of the multitudinous 

 spores ; and only the total destruction of the infested trees 

 avails to end the disease. 



To this order belongs Cordyceps (Fig. 317), parasitic on 

 the bodies of underground insects. The mycelium con- 



