THE SEXUALITY OF THE FUNGI. 45 



towards the latter until a union is effected. 1 This was observed and 

 confirmed several times. All the above facts are generally true of the 

 conidia also ; and Botrytis may be substituted for Isaria as the host 

 plant. 



After about eight days the above processes have resulted in the 

 formation of a vigorous mycelium and the formation of young peri- 

 thecia. The perithecium commences by the development of a lateral 

 branchlet, which becomes coiled two or three times, and divided by a 

 few septa ; this is the ascogonium. It fretuiently resembles that of 

 Ascobohis. 



Thinner hyphal branches now spring from below the ascogonium, 

 and envelope it by applying themselves closely to it, and branching and 

 dividing ; although one of these may grow out more rapidly at first, it 

 does not seem to more than hint at an antheridial branch. But very 

 often two or more arise together, and others soon follow in all cases. 



None of these branches copulate with the ascogonium. Although 

 Isaria branches may be close to and serve to nourish the hypha3 pro- 

 ducing the fructification, there is no doubt whatever that only the 

 hyphse from the Melanospora enter into the constitution of the fructifi- 

 cation. 



The details of the development of the perithecium wall from the 

 enveloping hyphee are interesting, but present nothing essentially new, 

 and need not be described here. 



Of the four or five cells into which the coiled ascogonium is divided, 

 the cell below the apex forms the ascogenous tissue. The terminal 

 cell above it becomes disorganised ; it is sterile, and soon disappears. 

 Its immediate neighbour (i. e. the cell below the apex) becomes cut 

 up by numerous septa in all planes, and forms an ascogenous core of 

 parenchymatous tissue. As this occurs, the internal layers of the now 

 dense envelope — produced by repeated ramifications and divisions of 

 the interweaving hyphae of the enveloping branches — become dis- 

 organised, deliquescent, and evidently then serve as nourishment for 

 the cells of the ascogenous core. 2 The proximal cells {i. e. those cells 

 between the ascogenous cells and the mycelium) of the ascogonium 

 also disappear, and the enveloping layers around them become elon- 



1 Cf. my description of the behaviour of a hypha of Pythium gracile, ' Quart. Journ. Mic. 

 Sc.,' October, 1883, p. 504 ; and also the remarks below on the behaviour of Spiroyyva in con- 

 jugation. 



- Cf. my description of the development of the perithecium in Meliola, 'Phil. Trans.,' 1883, 

 p. 592, &c. 



