26 NUCLEAB DIVISION 



In the beleutospore (i.e. tetraspore-mother-cell), the first 

 division is of a slightly higher type. The fusion-nucleus is 

 large, round and (when unstained) perfectly clear and homo- 

 geneous, but for its nucleolus, so that it looks like a vacuole : 

 it occupies almost invariably the middle of a cell. The dense 

 chromatin mass is loosened out into a kind of spireme which 

 becomes shorter and thicker; the nuclear membrane then 

 disappears, and the spireme thread splits longitudinally, though 

 the splitting is often indistinct. It then divides transversely 

 into segments which become arranged or strung out on a 

 spindle (sometimes, but more rarely, in an equatorial plate): 

 then the daughter nuclei are formed at the poles, and the next 

 division, which is homotypic, follows immediately (Harper and 

 Holden, 1903; Blackman, 1904). Hoffmann considered that in 

 Endophyllum Sempervivi he could count eight chromosomes 

 just before the reducing division. 



Since each of these nuclear divisions of the teleutospore- 

 contents is usually followed at once by the formation of a cell- 

 wall, there are obtained four cells which are generally super- 

 posed in a row. But Weir (1912) records a case in Coleosporium 

 Pulsatillae where they were arranged in a "tetrad," by which 

 word he means presumably (for he gives no figures) in a 

 square or tetrahedral manner. 



According to Dittschlag (1910) the nucleus of the spermo- 

 gonial hyphae is oblong and shows a slight chromatin network, 

 but usually without a nucleolus. After abstriction (for which 

 see Blackman, 1904), each nucleus enters again upon a resting 

 stage, and the chromatin network becomes looser. Each sper- 

 matium has a rather large nucleus, occupying about two-thirds 

 of the cell, showing a decided chromatin network, but almost 

 never a nucleolus. It has been frequently noticed that many 

 spermatia soon become binucleate, but the nuclei are sisters, 

 and this condition is merely a beginning of vegetative growth 

 which, however, usually aborts. 



In the secidia, the " fertile " (female) cells have a medium- 

 sized nucleus, with a fine chromatin network and a deeply 

 colouring nucleolus, as well as abundant finely granular proto- 

 plasm. When the conjugate nuclei have arisen, they lose their 



