238 LIFE HISTORY OF CLAVICEPS 



first group is further characterized by the fact that the ascocarps 

 are frequently associated with a more or less conspicuous growth 

 of the mycelium in which the ascocarps are imbedded in varying 

 degrees. This growth is known as the stroma and it may form 

 a rather compact mass of hyphae. Only two orders can be con- 

 sidered in each of these two groups. 



88. Order c. Hypocreales. — ^These fungi are distinguished by 

 their rather fleshy or membranous ascocarps and stroma, which 

 range in color from white to yellow, purple, scarlet and brown. 

 Numerous species are saprophytic while others are parasitic 

 upon higher plants, fungi and insects. Claviceps is a common 

 example of this group, causing the disease known as ergot in the 

 flowers of rye and other grasses (Fig. 145). The mycelium at 

 first spreads over the outer part of the pistil, rapidly forming 

 spores (Fig. 146, A, B) and exuding a sweet slimy juice, honey 

 dew, which is eagerly eaten by flies. In this way the spores are 

 carried away to infest other plants. The mycelium finally 

 completely absorbs the substance of the grain and grows into a 

 hard blue-black body several times larger than the grain (Fig. 

 145). This body, known as the sclerotium, remains dormant 

 during the. winter and in the spring groups of hyphae at various 

 points in the sclerotium grow out into rose-colored stalks that 

 terminate in globular heads (Fig. 146, C). These stalked bodies 

 represent the stromata as it appears in this genus. Numerous 

 ascocarps with minute openings are developed in the outer part 

 of globular head of the stroma (Fig. 146, D). The ascospores 

 germinate in the spring and infest the flowers of the grain. The 

 Chinese wonder, Cordyceps, is a related parasite that attacks 

 caterpillars, larvae of beetles and truffles. In the case of the 

 forms living upon insects, the parasite does not usually appear 

 until the spring, when they are in the pupa or cocoon stage. 

 At this time, the mycelium which flourishes in the tissues of the 

 host, sends up club-like bodies (Fig. 147), that bear the ascocarps 

 as in the case of the ergot. Among the important pests included 

 in this order are those causing the wilt disease of cotton, cowpea 

 and watermelon; the disease on currant, apple and pear trees; 

 and the claviceps of grain. 



