282 A TEXTBOOK OF THEORETICAL BOTANY 



The ascospores are carried to the grass plants at the time when the flowers 

 are maturing and find a lodgment among the floral parts. The hyphae formed 

 from them penetrate and ramify in the ovary, where they form a thick mass 



of tissue, which becomes hard and purple on 

 the exterior and forms a sclerotium. Mean- 

 while certain hyphae from within the tissues 

 of the ovary grow outwards through the ovary 

 wall and their exposed apices function as 



Fig. 274. — Claviceps purpurea. 

 Flowering spike of Arena 

 prateiisis bearing a black 

 sclerotium or ergot of the 

 fungus in place of one of 

 the flowers. 



Fig. 275. — Claviceps purpurea. Formation of 

 conidiospores. 



conidiophores and cut ofi^ small, spherical 

 conidiospores (Fig. 275). The efi'ect of this 

 fungal infection is to cause the enlargement 

 of the ovary, which at its upper end becomes rather spongy in character. 

 During the development of the conidiospores a sugary secretion is pro- 

 duced by the hyphae. Insects are attracted to this " honeydew " and 

 aid in distributing the conidiospores to other flowers where they can 

 produce fresh sclerotia. 



Sexual Reproduction 



After the conidial stage has reached its climax the sclerotium begins to 

 mature. The hyphae in the base of the ovary, instead of forming a loose weft 

 of filaments, become compacted into a dense mass which grows in length 

 and finally projects an inch or more from the ear of rye, which has by this 

 time ripened, carrying at its apex the remains of the mycelium which bore 

 the conidia. In this process the ovary is completely destroyed and the 

 sclerotium occupies its place, lying between the glumes of the rye spikelet. 



