-2 8 Journal of Agricultural Research vol. xx, no. 4 



with each other by the persisting, very narrow, central lumina (Pi. 52, B). 

 Magnus (20) designated this as encysted mycelium and regarded it as 

 being probably viable; although the degenerated condition of the pro- 

 toplasm where this is present, and more particularly the very frequent 

 absence of any contents whatsoever, would not argue for a high degree 

 of vitality. However this may be, the appearance of such swollen 

 mycelium suggests a pathological condition of the parasite rather than a 

 normal one. 



Beyond a statement by Wilson (37), quite impossible of interpreta- 

 tion in the light of the life history here presented, that the — 



content, cytoplasm, and the nuclei of the resting spores in the dormant condition cor- 

 responds to that of the plasmodium in the stage immediately preceding spore forma- 

 tion, 



there appear no cytological allusions in the literature on the alfalfa 

 parasite. However, certain details regarding the nuclear behavior in 

 Urophlyctis rilbsaameni have been given by Bally (2) , and the valuable 

 paper on U. hemisphaerica by Maire and Tison (21) contains a 

 brief account of nuclear changes in the congeneric parasite on Carum 

 incrassatum and Kundmannia sicula. 



The variability in size of the nucleus pointed out by these authors is 

 well exemplified also in Urophlyctis alfalfae, the larger and smaller dimen- 

 sions being here generally characteristic of certain stages in the develop- 

 ment of the organism. Thus, in the young primary turbinate cell, the 

 nucleus, which is subspherical in shape, commonly measures about 2 m in 

 diameter and is composed largely of refringent, nonstainable material and 

 a single, very conspicuous, deep-staining body (PI. 49, A, ta-tg). Later, 

 the nuclei may increase appreciably in size, even before their migration 

 into the secondary turbinate cells or into the young spore (Pi. 49, B, ta). 

 Considerable increase, however, appears to take place quite invariably 

 in the single nucleus of the young secondary turbinate cell, a maximum 

 diameter of 5 to 6 n being here attained before division occurs (Pi. 50, 

 tb-bx) . Division is initiated by the deep-staining body becoming elongated 

 and being drawn out into a spindle-shaped figure, which may be either 

 straight or distinctly cresentic, depending on the curvature of the portion 

 of the nuclear membrane to which it is laterally applied (Pi. 50, tbd). 

 This spindle-shaped structure appears to divide in the middle, yielding 

 two bodies similar to the original, which assume positions separated from 

 each other. A membrane is now formed between the two granules, 

 dividing the nonstainable material about equally; and when the two 

 hemispherical division products have rounded up, the structure of the 

 parent nucleus is reestablished, although pairs of sister nuclei can usually 

 be distinguished for some time by their nucleoles facing each other — a 

 figure that is by no means uncommon (Pi. 50, tab). 



We have never been able to make out in the nucleus at any stage in 

 the development of turbinate cells anything that would need to be inter- 



