212 



PROTOBASIDIOMYCETES 



[CH. 









■•:• :■ 



m 



Fig. i88. Uromyces Poae Raben.; conjut^nte divi<;ions 

 in aecidium, x 1330; after Blacliman and Fraser. 



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

 mitosis. In the spermatial hyphae of Gymnosporangium clavariaeforme, for 

 example, Blackman 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 Scirpi 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 

 speciosum 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 

 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 

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

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

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

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

 throughout their length. In the meantime centrosomes and spindle fibres 

 have appeared and characteristic gemini are recognizable on the spindle. 



Coleosporiuvi Senecionis\ mitosis in teleuto- 

 spores; after Amaud. 



phase. 



