Nov. 15, 1920 Crownwart of Alfalfa Caused by Urophlyctis alfalfae 309 



preted as a chromatin network. Occasionally in nearly evacuated sporo- 

 genous cells, where the attenuated condition of the cytoplasm permits 

 of more accurate study, strands were observed close to the periphery of 

 the refringent nonstainable portion; however, from their general appear- 

 ance and staining reaction, it is much more probable that these represent 

 overlying strands of cytoplasm. The chromatin material here seems to 

 be very largely if not completely concentrated in the conspicuous, densely 

 staining body, which may thus be regarded as a karyosome or chromatin- 

 nucleole. This mode of division presumably constitutes a type of ami- 

 tosis; and, indeed, with a nucleus of the structure described, mitosis of 

 the regular type is manifestly out of question. And yet the enlongated 

 spindle shape assumed by the nucleole suggests that perhaps division 

 here may involve some mechanism resembling in a rudimentary way the 

 apparatus associated with mitosis. The whole process bears consider- 

 able resemblance to that described by Kusano (13) as occurring in the 

 zoosporangia of Olpidium viciae. 



By repeated divisions the nuclei in the turbinate cells reach a number 

 of 10 to 20 before the latter has attained its final dimensions; and this 

 increase in number seems to involve usually a decrease in size, which may 

 sometimes be quite insignificant, or again quite considerable, but is 

 nearly always perceptible. Nutrition seems to have some influence on 

 the size of the nuclei at this stage, the turbinate cells found in recently 

 invaded tissues rich in protoplasm generally remaining relatively large 

 throughout, while those farther toward the origin of the cavity appear 

 to suffer the greatest reduction. 



The cytoplasm of the growing turbinate cells stains moderately deeply 

 and seems to have a uniform, finely granular or reticulate structure. 

 During the earlier stages of growth, a relatively large vacuole may usually 

 be distinguished near the proximal end. Perhaps this is later associated 

 with the insertion of a septum near the base of the cell that is probably 

 not always concerned in delimiting a uninucleated protoplast but appears 

 to serve more frequently in shutting off the protoplasm from the 

 evacuated hypha. Although the number of vacuoles of a size readily to 

 be observed may be increased during the later stages of growth to several, 

 the difference between the basal and distil ends never becomes consider- 

 able, the structure of the cytoplasm at the time of the insertion of the 

 peripheral septa being generally rather uniformly granular or finely 

 reticulate. The progressive evacuation of contents of both the peripheral 

 segments and the sporogenous cell brings about an attenuation of the 

 cytoplasm which, especially in the sporogenous cell, is associated with 

 the appearance of large vacuoles that ultimately, with the exception of a 

 few strands of cytoplasm, coalesce to fill the entire cell. 



As the isthmuses between the peripheral segments and the anlagen of 

 the young turbinate cells, as well as that between sporogenous cell and 

 resting spore, are considerably narrower than the nuclei, the latter 



