310 Journal of Agricultural Research vol. xx,No.4 



undergo some distortion in their passage through these communications. 

 The achromatin passes into the lumen of the connecting element as a 

 beaked extension followed by the chromatin-nucleole, which, too, is 

 drawn out in a conspicuous manner (PI. 49, C). The normal nuclear 

 structure is recovered when the material has reached, for example, the 

 flaring portion of the isthmus at the proximal end of the resting spore. 

 The result of the total protoplasmic movement is that in Urophlyctis 

 alfalfae the penultimate cells are either evacuated or in the process of 

 evacuation and that all elements more basal in position, hyphae as well 

 as peripheral segments and sporogenous cells, are always quite empty of 

 living material. 



Within the young, growing resting spore, the nuclei increase somewhat 

 in size; but much more marked is the immediate increase in size of the 

 chromatin-nucleoles, which at this stage measure 2 /1 in diameter, or 

 approximately half the linear dimensions of the nucleus. It is not 

 improbable that some nuclear divisions may take place. In living 

 material the resting spores show a beautifully vacuolate structure, the 

 vacuoles being numerous and relatively large (PI. 48, A-D, ra, rb). This 

 structure is apparently poorly preserved in the processes of killing, 

 embedding, and staining. Microtome sections stained with Flemming's 

 triple combination show the cytoplasm as having a dense reticulate 

 structure readily distinguishable, however, even in the earliest stages 

 from the cytoplasm of the turbinate cells by its greater affinity for 

 gentian violet. 



Later, during the maturation period, the cytoplasm of the resting 

 spores appears more loosely reticulate, and the nuclei assume still 

 greater dimensions, finally measuring 6 to 8 n in diameter (Pi. 49, D-F). 

 This increase in size is associated with the appearance of very minute 

 granules of chromatin more or less irregularly disposed near the periphery 

 of the achromatin mass and easily distinguished from the surrounding 

 cytoplasm by a marked difference in staining properties. In many cases 

 the arrangement in a definite reticulum is particularly pronounced 

 (PI. 49, F). Maire and Tison (21) report that in the resting spore of 

 Urophlyctis hemisphaerica certain nuclei become enlarged, their nucleoles 

 becoming vacuolated and giving rise to large masses of a substance 

 staining red with safranin which accumulate in the center of the spore. 

 Something similar seems to occur in the maturing resting spores of 

 U alfalfae. Plate 49, F, represents an early stage in the process, the 

 three nuclei shown in the center having become conspicuously enlarged, 

 the achromatin having partly lost its refringency, and the nuclear 

 contours having become less distinct. Later, as in Plate 49, E, the 

 chromatin masses are no longer distinguishable but appear to have been 

 transformed or replaced by vacuolate cytoplasm somewhat more attenu- 

 ated than at the periphery and inclosing in its meshes the numerous 

 granules of red-staining material that have presumably been derived 



