212 



PROTOBASIDIOMYCETES 



[CH. 



fication and in some cases it shows but few of the characters of normal 

 mitosis. In the spermatial hyphae of Gymnosporangium davariaeforme^ for 

 example, Blackmail has described a condensation of the nucleus to form 

 a deeply staining body out of which the nucleolus is squeezed. The chromatin 

 is drawn apart into two apparently homogeneous masses between which 

 a kinoplasmic thread represents the spindle. A similar process takes place 

 in the division of the conjugate nuclei in this and other forms, but the spindle 

 is generally recognizable somewhat earlier, at a time when the chromatin 

 of each nucleus still forms a single mass. As a rule the spindles of the 

 conjugate nuclei lie parallel one to another (fig. 188). 



Moreau, following Sappin-Trouffy, has recorded two chromosomes or 



./...,. chromatin masses formed from 

 each nucleus in various 'Uredi- 

 neae. Olive on the other hand 

 in Triphragmidium Ulmariae 

 and Uromyces Stirpi has found 

 a clearly defined spindle and 

 centrosomes and has succeeded 

 in recognizing several separate 

 chromosomes ; a similar state 

 of affairs has been recorded by 

 Christman for Phragmidium 

 spedosum so that it would ap- 

 pear that the different species 

 of rusts are at dissimilar levels 

 in this matter, though a further 

 study of carefully fixed material 

 might be undertaken with ad- 

 vantage. 



In all cases, however, the 

 divisions of the fusion nucleus 



Fig. 1 88. Uromyces Poae Raben.; conjugate divisions 

 in aecidium, x 1330; a'ter Blackmail and Eraser. 



Coleosporium Senecionis; mitosis in teleuto- 

 spores ; after Arnaud. 



of the teleutospore are much 

 more elaborate than those in the 

 vegetative cells and show some 

 of the characteristics of a meiotic 

 In Coleosporium (fig. 189) the fusion nucleus at first possesses a 

 -marked reticulum of interlacing threads. This undergoes a stage of 

 ^ration in one part of the nuclear area, which no doubt corresponds 

 > synapsis, and afterwards loosens out, increases in thickness and forms a 

 The spireme breaks up and its segments are seen to be double 

 .ghout their length. In the meantime centrosomes and spindle fibres 

 d and characteristic gemini are recognizable on the- spindle. 



