62 PHARMACEUTICAL BOTANY 



Order 5. Pyrenomycetales, the mildews and black fungi common as 

 superficial parasites on various parts of plants. To the black fungi 

 division of this order the Ergot fungus, Claviceps purpurea, belongs. 



LiPE History or Claviceps Purpttrea 



Through the agency of winds or insects the spores (ascospores or conidia) of this 

 organism are brought to the young ovaries of the rye (Secale cereale). They germi- 

 nate into long filaments called hyphas which, becoming entangled to form a myce- 

 lium, spread over the ovary, enter it superficially, secrete a ferment, and cause 

 decomposition of its tissue and the resultant formation of ayeUow-mucus substance 

 called honey-dew, which siurrounds chains of moniUform reproductive bodies known 

 as conidia. The honey-dew attracts certain insects which disseminate the disease 

 to other heads of grain. 



The mycelial threads penetrate deeper and deeper into the ovary and soon form 

 a dense tissue which gradually consumes the entire substance of the ovary and hard- 

 ens into a purple somewhat curved body called a sclerotium, or ofi&cial ergot — the 

 resting stage of the fungus, Claviceps. 



The ergot falls to the ground and in the following spring sprouts into several 

 stalked heads. Each (fruiting) head or ascocarp has imbedded in its surface nu- 

 merous flask-shaped invaginations called perithecia from the bases of which several 

 sacs or asci develop. Within each ascus are developed eight filiform spores (asco- 

 spores) which, when the ascus ruptures, are discharged and are carried by the wind 

 to other fields of grain, there to begin over a new life cycle. 



Class III. — Basidiomycetes, or Basidia Fungi 



This large class of fungi including the smuts, rusts, mushrooms, 

 gill and tooth fungi, etc., is characterized by the occurrence of a basid- 

 ium in the life history. A basidium is the swollen end of a hypha 

 consisting of one or four cells and giving rise to branches called sterig- 

 mata, each of which cuts off at its tip a spore. 



Sub-class A. — Protobasidiomycetes 

 (Basidium four-celled, each cell bearing a spore) 



Order i. Ustilaginales, the smuts. Destructive parasites which 

 attack the flowers of various cereals, occasionally other parts of these 

 plants. Ex. : Ustilago M'aydis, the corn smut. 



Order 2. Uredinales, the rusts. Ex.: Puccinia graminis, one of 

 the wheat rusts, living in the intercellular spaces of young wheat. 



