8 BOTANICAL GAZETTE [july 



That these nuclei are going into synapsis and not coming out is 

 shown by several features: (i) the extremely delicate character of the 

 threads, like those of the resting nucleus; (2) the fact that the 

 periphery of the reticulum as it contracts frequently preserves perfectly 

 the curved outline of the nuclear wall (fig. 12) ; (3) immediately after 

 synapsis the thread is somewhat shorter and thicker than previously 

 and appears to be continuous, while in the earlier contraction stages 

 we still have the appearance of a reticulum (fig. 13). 2 As the con- 

 traction progresses, the threads are gradually rearranged from an 

 anastomosing reticulum to a very long and continuous delicate thread. 

 The exact manner of this rearrangement could not be observed, but 

 one finds many transitions (fig. 14) from the anastomosing reticulum 

 of the resting nucleus to the closely coiled and apparently continuous 

 spirem of the synaptic knot (fig. 15). The contraction may take 

 place from one side of the nucleus, leaving the reticulum attached for a 

 time to the nuclear membrane at one point (fig. 13), or it may take 

 place simultaneously from all sides (fig. 12). A few threads of the 

 reticulum usually remain attached for a time to the nuclear membrane 

 while the contraction is going on. These are drawn in finally as the 

 synaptic ball becomes more compact. 



The small number of these intermediate stages found indicates 

 that they are passed through rather rapidly, the frequency of the occur- 

 rence of synapsis stages indicating, on the other hand, that this con- 

 dition is of considerable duration. 



No indication of a doubling or pairing of the threads during these 

 intermediate contraction stages could be observed, though they were 

 carefully searched for. Moreover, in the earliest stages of the synaptic 

 ball the thread appears to be as thin and delicate as in the reticulum, 

 which does not favor the view that a pairing has taken place. The 

 evidence, then, to far as it goes, is decidedly not in favor of a pairing. 



During these stages the nuclear membrane is often indistinct, 

 making it difficult to define accurately the limits of the nucleus. The 



2 This explanation assumes, of course, that the synapsis stages themselves are 

 normal and not due to artifact, as I presume all cytologists will now agree, although 

 Schaffner (29) apparently still entertains some doubt on the subject. The regularly 

 coiled arrangement of the thread in the synaptic ball appears to me to be one of the 

 best arguments against this stage being an artifact. Evidently a rearrangement of 

 the threads is going on as contraction proceeds. 



