DEVELOPMENT OF PLANTS 



237 



the one characterized by ascocarps that are only slightly opened 

 so that the asci are not as freely exposed to the air as in the 

 preceding orders and the other with closed ascocarps so that the 

 asci are exposed only on the decay of the fruit body. The 



Fig. 145. Fig. 146. 



Fig. 145. Head of rye infested by the parasite, Claviceps, which has 

 transformed several of the grains into black masses of mycelium known as 

 sclerotia. 



Fig. 146. Various phases in the life history of Claviceps: A, a young 

 grain or pistil. infested with the parasite. B, enlarged view of the mycelium 

 as it appears on the surface of the pistil, showing the formation of numerous 

 spores. C, the hyphae of a sclerotium growing out and forming several 

 purplish stalks, each capped with knob-like clusters of ascocarps. D, en- 

 larged Sectional view of one of these knobs, showing numerous ascocarps 

 on the periphery. E, one of the ascocarps enlarged, as, asci. F, an ascus 

 containing eight thread-like ascospores. 



