S6 



rendered probable "by what we know of other groups of plants. 

 In the simplest plants which liave been investii^ated from 

 Viiis standpoint, the position of reduction in the life 

 history seems to he at the first divisions of the fusion nu- 

 cleus, as is described in Coleochaete (ALLEN, '05), certain 

 desmids (KLEBATCI, '91), SpiroF.LT^-a f CrOCEELRV/SKT^ '00), and in 

 I/T;ocomycetes (laiAlIZLIir, '07) . Beginning with the simple 

 Bryopliytes, the familiar Archegoniate series shows a pro- 

 gressive removal of the point of reduction from the point 

 of fusion of the sexual nuclei. These and other examples 

 seem to show that there is a general tendency thi'oughout 

 the planj; kingdom to prolong the diploid condition of the 

 nucleus through the greater part of the life history. 



ITowhere is this more plainly shovm tlian in the Uredi- 

 neae (ELACKIIAII, '04, BLACKIIAIT and ERASER, 'Of,, CKRISTilAM, 

 •07) . This group is characterized by a succession of 

 phases, or generations, whicji httve been shown by Christman 

 (•06, '07) to be morphologically equivalent, thoug}i each 

 ends in a distinct form of spore. Now nuclear association, 

 which has been reg&xded as tlie equivalent of fertilization 

 in this group, occurs, in all foi^ms in which tlie aecidial 

 stage is present, in those cells of tlie mycelium which give 

 I'ise to tlie aecidium. The process of nwnerical reduction 



