﻿1903] PRIMARY NUCLEUS IN SYNCHYTRWM 413 



*- showing the chromosomes at the two ends of the spindle. They 



are probably four in number, although we do not assert this with 

 I certainty. After the polar migration of the chromosomes the 



whole spindle lengthens much, giving a peculiar distorted figure 

 similar to that found in the nuclei of A, Bliti, and the telophase 

 is of similar nature to that described for that fungus (Stevens, 

 '99), The spindle fibers fall together in the center and divide, 

 giving rise to the independent daughter nuclei. 



This mitosis agrees well in late anaphase with that of many 

 other fungi, conspicuously so with Albugo. In many other 

 respects it is unique. The early dissolution of the membrane 

 and the persistence of its remains as a granular halo around the 

 metaphase and anaphase figures is a new phenomenon, as is also 

 the mode of spindle formation. The spirem also differs from 

 any previously described, and the behavior of the nucleolus is 

 unique; while the disposition of the chromatin in resting and 

 early prophase conditions is exceptional. 



The great size of the nucleus led to an inference that the 

 mitosis would present, perhaps more clearly than any other type 

 of fungus, the details of spindle formation. This inference was 

 unfounded, since the shrinkage of the nucleus preparatory to 

 mitosis reduces the spindle to moderate dimensions. Moreover 

 the stages are rare to find. Hundreds of samples were examined 

 showing no trace of mitosis, while a ver}' few leaves of the host 

 plant were found exhibiting good stages. When a block of 

 good material is secured it gives abundant cases, however, to 

 prove the existence of mitosis. Still, as there can be obviously 

 only one primary division in each sorus it is an exceedingly slow 

 task to complete a series. All of the figures represented come 

 from sori bearing only one nucleus, and unquestionably represent 

 primary division. Occasional views of the second and succeeding 

 mitosis were had, but here the subject becomes much complicated 

 and discussion is reserved for a later paper. 



The significance of the facts observed, such as the enlarge- 

 ment of the nucleus and its subsequent shrinkage, the peculiari- 

 ties of mitosis, the chromatin changes, etc., will be better 

 interpreted when the other peculiarities in the cytology of this 



