6 TEXT-BOOK OF FUNGI 



contain a single nucleus during the early stage of their 

 life-history. At a later stage the cells in both groups 

 become binucleate. This is considered by Harper as 

 evidence of phylogenetic affinity between the two groups, 

 a point that had previously been suggested from a morpho- 

 logical standpoint. 



Results are as yet too few in number and too contra- 

 dictory to admit of the formulation of a new scheme of 

 affinity or classification based on cytology. Nevertheless the 

 disciples of this school are very sanguine, and have already 

 done thoroughly good work, much appreciated by all ranks 

 of mycologists. Perhaps it is doubtful whether any real 

 benefit is to be derived from the lengthened theoretical 

 suggestions so conspicuous in cytological papers. Another 

 feature is the contempt for morphological evidence. On 

 this point, in criticising a suggestion of affinity from a 

 morphological standpoint, Davis says : ' Resemblances 

 of form have very little value in such comparisons, and 

 relationships must be traced through agreement in the 

 details of protoplasmic activities.' The same author 

 again, in the same paper, emphasises the above idea as 

 follows : ' Form resemblance must be in complete 

 harmony with cytological conditions to have weight.' 



If true, this is very serious indeed. The evidence of 

 descent, supposed to have been obtained from an in- 

 vestigation of fossil plants and animals, etc., but perhaps 

 it is not necessary to dilate on this point. 



The discovery by Klebs of the influence of food and 

 surroundings in determining the production of a particular 

 kind of reproductive organ, or of sterility, is of primary 

 importance. He has shown that it is possible to produce 

 at will zoospores, antheridia, or oogonia in certain fungi, 



