304 Journal of A gricultural Research vol. xx. No. 4 



occupying a position on the side or toward the base of the turbinate cell, 

 the protuberance will invariably take place at some point along the edge 

 closest to the apical end of the turbinate structure ; while in the segments 

 on the apical end the protuberance usually occupies a middle position. 

 By the movement of the nucleus and part of the cytoplasm into the pro- 

 tuberance, the tip of the latter becomes somewhat distended. The con- 

 stricted position now rapidly elongates, resulting in the formation of an 

 attenuated hypha, uniform in thickness and approximately 0.5 fx'va diam- 

 eter (PI. 48, A-D). The transfer of protoplasm from the peripheral 

 segment to the distended termination continues for some time, until the 

 former has been completely evacuated (Pi. 48, B, D, la). 



The elongation of the hypha involves a translatory movement of the 

 termination in a forward direction, from which, however, it may be de- 

 flected by a host cell wall, or even reflected back toward the cuticular 

 wall (PI. 49, B, tba). Ultimately elongation ceases, and the terminal 

 distension develops into a turbinate cell entirely similar to the original 

 product of infection, the single nucleus dividing repeatedly to reproduce 

 the coenocytic condition and the branching haustorial process developing 

 from the apical projection, which becomes observable at an early stage 

 during the period of hyphal elongation. 



The proliferation of secondary turbinate cells, which tends to be more 

 abundant from the expanded apical end than from regions more nearly 

 basal, thus involves a certain number of lenticular uninucleated masses 

 of protoplasm, always peripheral in position. The larger remaining por- 

 tion of the contents of the original turbinate cell is consequently not 

 concerned in this process. It may conveniently be designated as the 

 sporogenous cell and always embraces the contents along the longitudi- 

 nal axis of the spore and as much peripheral protoplasm as is not involved 

 in the peripheral segments. The contents of the sporogenous cell func- 

 tions in giving rise to a resting spore in the manner described in the fol- 

 lowing paragraph. 



vSooner or later after the segmentation of the turbinate cell has been 

 initiated, the axial haustorial prolongation buds terminally to produce 

 a small globose swelling, which, when it first becomes noticeable, has no 

 demonstrable irregularities on its surface. Later when the swelling or 

 young resting spore has attained a diameter of perhaps 5 fi (PI. 48, D, 

 rb), there are proliferated along a zone midway between the equatorial 

 region and the distil pole from 9 to 15 slender, unbranched, minute proc- 

 esses. The swelling continues to increase in size until it attains the 

 dimensions of the resting spore (about 25 to 35 by 40 to 50 /*), growth in 

 the earlier stages being due mainly to the transfer of protoplasmic con- 

 tents from the sporogenous cell through the axial haustorial element 

 but later quite largely by the assimilation of food material from the host. 

 Although the surface of the resting spore is rendered impervious by the 

 deposition of a thick wall during the later stages of enlargement, such 



