T907] CHRIST MAN—MORPHOLOGY OF THE RUSTS 91 



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A careful study of the telcutosori of Puccinia podophyUi revealed 

 that nuclear migrations are quite common here. This was particu- 



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larly true at the base of the spores and in the margins of the sori. 

 The nucleus forms a beak which penetrates into a neighboring cell 

 {fig. 13). This projection elongates, forming a sort of thread as the 

 material of the nucleus passes over into the foreign cell (fig, 14). 

 At this stage the elongated portion of the nucleus loses its normal 

 structure and becomes densely stained with the red of the triple stain. 

 This dense staining is figured by Miehe and Schurhoff, and appears 

 in figures by Blackman. The portion of the nucleus which has 

 passed the wall now begins to enlarge {figs, i^, 16). In the latter 

 figure there is evidence that the nucleus migrates from one cell of a 

 hypha to the next, while in the other cases the nuclei appear to be 

 migrating from one hypha to another. 



Sections which show all the nuclei of the cells concerned in the 

 migration are hard to obtain. By studying the series of sections to 

 which fig. 14 belongs, it was found that cell a contained two nuclei, 

 ^ while cell b contained but one. From this it seems plain that in 



this case there is a migration between normal vegetative cells of the 

 sporophyte where no fertilization can be assumed. This would 

 result in the production of a cell with three nuclei. Indeed this con- 

 dition is quite common {fig. if). 



The only interpretation possible here seems to be the one given by 

 Miehe, that this condition is entirely pathological and possibly due 

 to the wound produced at the time of fixation. The fact that three- 

 and four-nucleated spores are often found has been pointed out by 

 Sappin-Trouffy and Blackman. If such spores result from patho- 

 logical nuclear migration, this would indicate that the pathological 

 condition which produced the migration must have occurred a con- 

 siderable time before fixation, which is hardly an adequate hypothesis. 

 The wounding in preparation for the killing solution perhaps explains 

 wtU enough figures in which the nuclei are in process of migration^ 

 The fact that the migrations w^ere observed in many cases in a sort of 

 rudimentary paraphysis bounding the pustules is perhaps significant. 

 It undoubtedly helps to explain certain conditions in the cuplike 

 aecidia where isolated binucleated cells are often found in the older 

 pustules quite out of range of the bases of the rows of spores where 

 the fertilization processes occur. 



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