NUCLEAR PHENOMENA ii 



probability brought about in the basidium itself during the two 

 successive bipartitions of the fusion nucleus. The two original 

 nuclei in each basidium are not sisters but are very remotely 

 related to one another. Investigation seems to show that they 

 are derived by a long series of successive conjugate divisions from 

 a pair of nuclei, the two members of Avhich come to lie side by 

 side prior to the development of the fruit-body. The nucleus 

 which wanders into a spore soon divides into two after its entry 

 so that each spore becomes binucleate.^ As soon as the spore 

 germinates, these two nuclei enter the germ-tube, where they divide 

 at different rates and not in a conjugate manner.- By further 

 nuclear divisions the germ-tube comes to contain more than eight 

 nuclei in Hypholoma perplexum, and up to thirty in a species of 

 Coprinus.^ However, so far it has not been found possible to 

 determine exactly where the first pair or first pairs of nuclei come 

 into existence.'* In one group of Basidiomycetes^the Uredineaj — 

 Blackman ^ and others *> have observed that each pair of nuclei 

 which undergo fusion in the teleutospore, is derived by a long 

 series of successive conjugate divisions from a pair of nuclei brought 

 into existence by the conjugation of neighbouring mycelial cells. 

 The wall between the two cells becomes perforated and the nucleus 

 of one cell wanders into the other cell. It yet remains to be 

 decided whether or not anything of a similar nature occurs in 

 the Hymenomycetes. In this connection some interesting dis- 

 coveries may be in store for us. In species of Coprinus, &c., where 

 it has been found possible to obtain fruit-bodies from the mycelium 

 produced from a single spore, doubtless cross- fertilisation between 

 two individual mycelia either does not occur or is not necessary 

 for the completion of the life-cycle. Whether or not cross- 



^ Miss S. P. Nichols, "The Nature and Origin of the Binucleated Cells in some 

 Basidiomycetes," Trans, of the Wisconsin Acad, of Sciences, Arts, and Letters, vol. xv., 

 1904, pp. 30-70. Abstract in Bot. Zeit., Abt. II., Bd. LXIV., 1906, p. 266. 



' Ibid. 3 Ihid. " Ibid. 



^ V. H. Blackman, " On the Fertilisation, Alternation of Generations, and 

 General Cytology of the Uredinese," Ann. of Bot., vol. xviii., 1904. 



" A. H. Christman, "Sexual Reproduction in the Rusts," Bot. Gaz., yo\. xxxix., 

 1905; also E. W. Olive, "Sexual Cell Fusions and Vegetative Nuclear Divisions 

 in the Rusts," Ann. of Bot., vol. xxii., 1908. 



