THE FUNGI : ASCOMYCETES AND BASIDIOMYCETES 287 



coloured brown. Besides these there are small hyphae with dense protoplasmic 

 contents and still smaller ones which do not stain so densely. It is from the 

 first of these types that the tissue of the stroma becomes differentiated, while 

 the second type eventually gives rise to the perithecia, and the third type 

 forms the superficial layers and the conidiophores. 



The rigiditv of the stroma is greatly increased by a system of interlocking 

 effected by the large-celled hyphae. Despite the mechanical rigidity obtained 

 in this way the walls of these cells are no thicker than those of the smaller 

 hvphae which form the reproductive bodies. 



On the edge of this central zone the small hyphae pass out into the peri- 

 thecial zone. Those which are larger in diameter, however, do not continue 

 beyond the inner part of this zone, while the very fine hyphae continue beyond 

 it into the fourth zone, where they give rise to the superficial boundary. 



Asexual Reproduction 



Some of the thin hvphae of the superficial zone instead of forming a 

 layer running parallel to the surface, grow outwards to the exterior. These 

 hyphae are binucleate and somewhat flattened, and are made up of elongated 

 cells. Each hvpha branches once or twice and gives rise to conidiospores 

 which are developed in clusters (Fig. 281). The conidiospores are small, 



. ^- 



Fig. 281. — Hypoxylon coccineum. Section through stroma 

 showing superficial conidiospores. 



oval and colourless. They are liberated in great numbers during the summer 

 months and give rise to fresh mycelia. 



Conidiospores are not exclusively produced on the surface of the stroma. 

 They are also produced as outgrowths directlv from the mvcelium. In 

 addition, it is not unusual to find conidiospores developing inside young 

 perithecia or possibly in those which would otherwise fail to mature. 



Sexual Reproduction 



The first indication of the formation of a perithecium is the coiling up 

 of the end of one of the small hyphae lying in the lower region of the 



