THE FUNGI : ASCOMYCETES AND BASIDIOMYCETES 283 



This sclerotium is called the ergot. It is a hard body with a purple 

 or black outer coat and a white interior. In this form the Fungus passes 

 the winter, usually in the ground when the flower stalk has withered. In the 

 spring it begins to grow by producing a number of fleshy stalk-like projections, 

 each of which terminates in a globular head and is termed a stroma (Fig. 276). 

 These stromata are yellowish-brown in colour. When mature the globular 

 heads are seen to be covered with slightly raised papillae, surrounding pores 

 which are really the ostioles of perithecia. In a longitudinal section through 

 the head these perithecia will appear as flask-shaped cavities arranged in a 

 single layer all over the surface of the head (Fig. 277). 



Fig. 276. — Claviceps purpurea. Two sclerotia 

 germinating to produce stalked stromata. 



(Fro)n the Museum of the Pliarynaceutical Society , per Dr ll'allis.) 



Fig. 277. — Claviceps purpurea. Longitudinal 

 section through a stroma showing stipe 

 and peripheral zone of perithecia. 



The sex organs are formed in regular positions in the perithecial heads 

 and produce a layer. Each originates from a single, elongated, multinucleated 

 hypha which is rich in cytoplasm and arises from a vegetative cell. The 

 terminal cell of this branch swells and the nuclei in it divide and arrange 

 themselves in pairs, forming a dicaryon. From the positions of the nuclei, 

 branches arise, each of which is unicellular and each receives a single 

 dicaryon. This branch then elongates considerably and nuclear division 

 ensues. The branches then bend towards one another in pairs, one of a 

 pair being stouter and thicker than the other, which is slender and elongated. 



