ADDENDA 413 



Blackman, however, does not agree to this view, and 

 supports his previous statement as follows : 



' If, however, the view be accepted that the fertile cells 

 of P. violaceum represent female gametes, which are now 

 fertilised by vegetative cells instead of by male cells (the 

 now functionless spermatia), it follows that the cells which 

 fuse in P. speciosum since the structure and development 

 of the adcidium is exactly the same in the two cases also 

 represent female cells which now conjugate in pairs. By 

 such a very simple interpretation the two processes are 

 reduced to a common term. The two species of Phrag- 

 midium are then seen to be merely two different methods of 

 dealing with the same problem fertilisation in the absence 

 of the male cell. In the one case the male cell is replaced 

 by a vegetative cell ; in the other by another female cell. 



* If, on the other hand, Christman's view of the behaviour 

 of P. speciosum be accepted, it must also apply to P. viola- 

 ceum, and it leads to the unsatisfactory conclusion that the 

 fertile cells here also represent undifferentiated gametes, 

 which for some obscure reason have given up fusing in 

 pairs, and now fuse with vegetative cells instead. 



'The view put forward above obviously explains the 

 relation of the two processes throughout the group, and 

 has the further advantage of giving a reasonable explana- 

 tion of the structure and occurrence of the spermatia, 

 which in Christman's view are left out of account. 



' That the conjugation of female gametes may take place 

 in the absence of the appropriate male cell is shown clearly 

 by the author's studies on Humaria granulata, where, in 

 the absence of the antheridium, the female nuclei of the 

 ascogonium fuse in pairs.' 



Further investigations by Blackman and Fraser have 



