﻿4o8 BOTANICAL GAZETTE [june 



ited to a description of a series of stages, all clearly pertaining 

 to true mitosis in the primary nucleus. 



De Bary and Woronin observed and have described in beauti- 

 ful detail the entrance of Synchytrium into the host cell. From 

 this point it is easy to follow the cytological changes. The 

 cytoplasm of the invading parasite stains deeply, and is clearly 

 recognized imbedded in the lighter cytoplasm of the host cell. 

 For some time both the nucleus and the cytoplasm of the host cell 

 persist, but eventually they disappear, the parasite in the mean- 

 time increasing rapidly in size, A moderately early stage of 

 development is represented \Vi fig. /, which show^s the granular, 

 darkly staining mass of cytoplasm, spherical in form, and with a 

 relatively large nucleus and nucleolus.. Adjacent host cells 

 exhibit nuclei and chloroplasts, thus admitting of comparison as 

 to their relative size. At this and other early periods of devel- 

 opment the nucleolus is large, usually solitary, homogenous in 

 appearance, and surrounded by a thick darkly staining wall which 

 is probably largely composed of a layer of linin laden with 

 chromatin. Encasing the nucleolus is a mass of chromatin 

 usually forming a continuous covering, and in places collected 

 into irregular heaps and lumps. Occasional strands of chro- 

 matin connect the nucleolus, which is usually centrally placed, 

 with the nuclear membrane. Chromatin is also found distributed 

 in apparently disconnected globules of varying size, studded 

 thickly over the inner surface of the nuclear membrane. 



The parasite rapidly enlarges to occupy completely the host 

 cell, which soon becomes enormous in size as gall-formation 

 proceeds. A single host cell which normally averages less than 

 15/i in diameter after occupation by the parasite usually attains 

 a diameter of loo/^ or more. As the cell grows the nucleus 

 grows, reaching at its maximum a diameter of 3 5 /a. During this 

 enlargement the character or structure of the nucleus changes 

 somewhat. The nuclear membrane becomes thicker and more 

 conspicuous. The globules of chromatin studding its inner sur- 

 face increase in number and size, and more connections are 

 established between the chromatin surrounding the nucleolus 

 and that of the periphery. 



