NUCLEAR DIVISION 25 



next in order. Even, therefore, if the spermatid could produce 

 an infection, their feeble aid would be wasted at such a time of 

 rejuvenation. 



(8) There is also to be considered the fact that the 

 spermogones and spermatia of the Uredinales resemble those of 

 the Collemacea?, which have been shown by Stahl (1877) and 

 Baur (1898) in all probability to fulfil the male function 1 . It 

 may be pointed out, in this connection, that the great similarity 

 of the spermogones to the pycnidia of the Ascomycetes has 

 been too much ignored, and that its significance is not yet fully 

 appreciated. In the Ascomycetes the pycnospores in most 

 cases undoubtedly act as conidial forms, and have lost all traces 

 of their primitive male function — in the Uredinales the sper- 

 mogones have equally lost their function, but have not taken 

 on the secondary role of conidia : it may be suggested that the 

 latter are otherwise well provided for in that respect, and hence 

 feel no necessity for additional conidia. The spermatia of 

 Polystigma rubrum are, however, functionless either as male 

 cells or as conidia (Blackman and Welsford, 1912). 



Nuclear Division in the Uredinales. 



This is always of a simple type, not primitive, but reduced. 

 The number of chromosomes seems to be always somewhat 

 uncertain, and the chromatin forms masses which vary in 

 number from one to four. In the ordinary vegetative division, 

 which may be regarded as approaching rather to the nature of 

 amitosis, the nuclear membrane disappears, the nucleolus is 

 extruded, and the chromatin masses are drawn apart on a kind 

 (>f rudimentary spindle to form the daughter nuclei. In syn- 

 karya, the two paired nuclei in a cell are almost always in the 

 same stage of division at the same moment, and the four 

 resulting daughter nuclei move apart in such a way that the 

 two nuclei in each daughter cell are never sister-nuclei (Hoff- 

 mann, 1911). 



1 A remarkable instance in Collema, though outwardly not at all resembling 

 the case of the Uredinales, is described by Bachmann (1912). 



