﻿4IO BOTANICAL GAZETTE ' [june 



cytoplasm. The replacement of the nuclear wall by this gela- 

 tinous substance is a process which can be followed closely from 

 its inception {^fig- 5) to the later stages of mitosis {fig. 14)^ The 

 inner boundary of the nuclear wall remains definite until mitosis is 

 well advanced {fig. 10). The first indication of the dissolution 

 of the nuclear wall is evidenced by the darker staining of the 

 cytoplasm Immediately in contact with the wall [fig. 4), This 

 darkly stained region rapidly grows to a layer of gelatinous 

 consistency in which the cytoplasm is of finer mesh and tends to 

 be more granular. Changes very similar to those noted accom- 

 pany both dissolution and building up of walls in Albugo 

 (Stevens, '99). As the character of the nuclear membrane 

 changes a marked shrinkage in the size of the nucleus occurs, 

 possibly directly induced by the altered osmotic relations. A 

 decrease from 40 to 20 /x is not unusual in this first step toward 

 mitosis. The nucleolus, dissolution of which had proceeded far 

 in fig. J, now completely disappears. The line bounding it, 

 which seemed a husk of chromatin rather than a definite mem- 

 brane, vanishes, and the nucleolar substance, which was much 

 wasted by the one'large and many small vacuoles, is no longer to 

 be seen. Occasional small globules, staining like vacuoles of the 

 nucleolus [fig. j), may be found in the spirem and constitute the 

 only remaining trace of the nucleolus {fig. 7). 



The chromatin undergoes a change as striking as that of the 

 membrane and nucleolus. Formerly coarse and lumpy {fig-j)^ 

 its globular masses become much more numerous and relatively 

 smaller {fig, 5). They then appear to elongate, the numerous 

 globules being replaced by rods crossed and tangled in inextri- 

 cable confusion. Ftg. 6 represents a condition where the globules 

 have partially changed to the elongate form, while fig- 7 shows 

 the completion of this phase, resulting in what must be regarded 

 as the typical spirem of this primary division in Synchytritim 

 decipiens. It is characterized by fine even threads of chromatin, 

 uniformly distributed throughout the nucleus, yet tangled and 

 intertwined in a most complicated way. The dots in the figure 

 represent end views of the chromatin threads, and the lines the 

 same from a side view. The slightest change In focus brings 



