DEVELOPMENT OF PLANTS 



217 



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 



Fig. 153. 



Fig. 154. 



Fig. 153. Head of rye infested by the parasite, Claviceps, which has 

 transformed several of the grains into black masses of mycelium known 

 as sclerotia. 



Fig. 154. Various phases in the life history of Claviceps: A, a young 

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

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

 numerous spores. C, the hyphae of a sclerotium growing out and form- 

 ing several purplish stalks, capped with knob-like clusters of ascocarps. 

 D, enlarged sectional view of one of these knobs, showing numerous asco- 

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

 ascus containing eight thread-like ascospores. 



