156 BOTANICAL GAZETTE [august 



Intercellular karyogamy is the term applied to that condition in the - 

 basidiomycetes by which the nuclei are associated in pairs throughout long 

 periods of vegetative activity, but finally fuse in the basidium or teleutospore 

 at the end of the vegetative phase in the life history. The fusion is believed 

 by a number of investigators to be a sexual act, and the association of the 

 nuclei in pairs for so long a time is considered an extension of the period 

 when the gamete nuclei were really differentiated. There are several 

 accounts of the fusion of nuclei in the basidium, several botanists claiming 

 that only two nuclei enter this structure and fuse, while others (Wager and 

 Rosen) have reported as many as three, four, six, and eight concerned with 

 this phenomenon. Ruhland^^in a recent paper throws the weight of his 

 studies upon several of the hymenomycetes in favor of the predominance 

 and possible universality of two primary nuclei entering the basidium and 

 there uniting to form the secondary basidium nucleus, which later divides 

 just previous to spore formation. His conclusions thus accord with the 

 recent paper of Harper (Box. Gaz. 33 : i. 1902). We do not yet know when 

 the paired condition of the nuclei arises in the life history of any basidiomy- 

 cete, and this is a very important period, for events may occur at that time 

 which make these nuclei physiologically gametes. However, it is much to 

 know that these pairs of nuclei lie in a definite path of development which 

 ends with their final fusion in the teleutospore and basidium. The more 

 thoroughly we understand these processes in the basidiomycetes the sharper 

 appears the distinction between them and nuclear fusions in the ascus. The 

 two events have no morphological relation to one another. That in the ascus 

 is certainly not concerned with gamete nuclei, whatever may be its physio- 

 logical significance. — B, M. Davis. 



=^«RuHLAND, W., Zur Kenntniss der intracellularen Karyogamie bei den Basidi- 

 omyceten. Bot. Zeit. 59:487-206,//. 7. 1901. 



