294 BOTANICAL GAZETTE [april 



(figs. 7, 23, 44, 45). The cell plate forms late; it is most definite 

 after the fibers have taken their final position (figs. 6, 7, 8, 

 41, 45). These mitoses are similar to that described for Abies 

 balsamea (9). 



The cell plate is evidently associated with the formation of the 

 cell wall. In fig. 45 the arched fibers remain only at one side, but 

 here there is a distinct cell plate and the cell wall is curved outward 

 to meet it. When the wall is formed the fibers disappear. In 

 many cases no cell plate could be seen (figs. 5, 21, 22, 23), and the 

 division in the cytoplasm is continuous with the end of the fibers 

 (fig- 25). 



There is abundant evidence that the achromatic fibers are 

 definite structures which change their position. The fact that 

 there are groups of spindle fibers which have no immediate con- 

 nection with nuclear membranes or chromosomes is further evi- 

 dence for their individuality (fig. 8) . 



Secondary divisions have markedly different characters. A 

 polar cap is formed during prophase (fig. 48); the spindle fibers 

 are more strongly developed during metaphase (fig. 38) ; the cell 

 plate forms early (figs. 47, 49), and the spindle fibers retain their 

 original positions. The similarity of secondary divisions in the 

 first and third primary derivatives is illustrated by figs. 47 and 49. 



Chromatic extrusions 



In the early stages of the gametophyte, darkly staining bodies 

 occur in the cytoplasm. When the primary nucleus is in the rest- 

 ing stage, these bodies appear as spherical masses surrounded by 

 a clearer area (fig. 34) ; when the primary cell is in active mitosis 

 these extrusions become fragmented (fig. 35). These bodies 

 originate from wandering chromosomes which escape during mi- 

 tosis. Separate chromosomes are found near the primary cell wall 

 during metaphase (fig. 36). Evidently these never take part in 

 cell plate formation. They contract into spherical masses and 

 wander into the cytoplasm. In other cases, during late anaphase, 

 several chromosomes prematurely contract to form a more or less 

 compact mass, thereby separating themselves from the chromo- 

 somes which later undergo a similar change (fig. 3). 



