COPRINUS STERQUILINUS 



159 



eleven in number, are all marked by arrows and, owing to the 

 existence of these fusions, the various hyphae are connected 

 together. At the rate of 

 eleven hyphal fusions to 

 each 0-15 square mm., 

 a layer of mycelium 

 Uke that shown in Fig. 

 89, but discoid and 6 cm. 

 in diameter, would con- 

 tain approximately 

 200,000 hyphal fusions. 

 Clearly, therefore, if 

 one wishes to under- 

 stand the morphology 

 and physiology of a 

 mature mycelium of C. 

 sterquilinus, it is neces- 

 sary to grasp the funda- 

 mental fact that the my- 

 cehum is a fine-meshed 

 network of hyphae ex- 

 tending in three direc- 

 tions of space. 



The hyphal fusions 

 which have just been 

 described have nothing 

 to do with sex ; for 

 (1) in homothallic 

 Hymenomycetes, such 

 as C. sterquilinus, the 

 change from the haploid 

 to the diploid condition 



Fig 



89. — Coprinus sterquilinus, a homothallic 

 Hymenomycete. Camern-lucida drawing of an 

 older part of a mycelium in the diploid phase, 

 growing in cleared dung-agar in a Petri dish. 

 Mycelium seen in optical section. To show that 

 the mycelium is a three-dimensional network : 

 a a, b b, and c c, three hyphae which grew 

 radially outwards from the centre of the my- 

 celiimi. These hyphae, which bear clamp- 

 connexions, as at d d, and also contain some 

 plain septa, as at e, are connected together by 

 means of anastomoses effected by brancli hyphae. 

 There are eleven fusions to be seen in the drawing, 

 and the position of each of them is indicated 

 by an arrow. Area of mycelium, 0- 15 square mm. 

 Drawn by A. H. R. Buller and Ruth Macrae. 

 Magnification, 187. 



is not necessarily pre- 

 ceded by any hyphal fusion whatever, and (2) hyphal fusions 

 continuously increase in numbers long after the whole mycelium has 

 become diploid, i.e. when the nuclei are already in pairs and are 

 dividing conjugately. 



