Nichols, A morphological study of Juniperus communis var. depressa. 231 



cannot be considered as completed until tlie "half chromosomes 

 derived from the male and female nuclei respectively fuse together 

 at the poles of the first segmentation spindle". In the European 

 J. communis Noren (1907, p. 43) descrihes a rather peculiar con- 

 dition. He writes: "Die kettenförmig- mit einander verbundenen 

 Pseudonucleolen verschmelzen schließlich mit einander (1. c, fig. 78), 

 wodurch dicke, unregelmäßige Fäden entstehen. Auf diesem Stadium 

 können noch die den resp. Kernen zugehörigen Chromatingruppen 

 deutlich unterschieden werden, also auch noch nachdem die Mem- 

 branen zwischen den Kernen völlig verschwunden sind". 



The behavior of the chromatin in J. communis depressa is 

 very similar to that observed by the above mentioned writers, but 

 no indications were found that the spirems originate, in the manner 

 described by Noren, from the "melting together" of the pseudo- 

 nucleoli. For one or two days after the union of the male and 

 female nuclei the fusion nucleus to all appearances continues in a 

 resting condition. Then there begin to appear in the nucleus 

 numerous more or less connected, moniliform threads which exhibit 

 a beautiful differentiation into chromatin and linin (flg. 103). These 

 Strands run all through the nuclear cavity, and, while it is im- 

 possible to make out with certainty whether two spirems are 

 present at this time, such is presumably the case. The threads 

 soon draw away from the nuclear membrane, become more closely 

 coiled, and in the stage represented by fig. 104 it can be clearly 

 seen that two distinct spirems have been organized. At the same 

 time the whole band comes to stain uniformly, and the nucleolus- 

 like structures disappear. The infrequency with which the con- 

 dition described here has been observed is easily accounted for 

 by the difficulty with which suitable preparations are obtained. 

 Fig. 104 represents the only instance, out of over 2000 archegonia 

 examined in which this stage might be looked for, where it 

 is possible to distinguish the male and female elements in the 

 fertilized egg. 



Segmentation into chromosomes takes place rapidly and ap- 

 parently in the usual manner, the chromosomes become oriented at 

 a common equatorial plane (fig. 105), and a broad, multipolar 

 diarch spindle is organized. At this period coarse, granulär threads 

 are sometimes seen in the protoplasm of the nucleus outside the 

 spindle, but their relation, if any, to the formation of the spindle 

 in obscure (cf. Ferguson 1904, figs. 228 — 230). The multipolar 

 diarch quickly becomes bipolar, and the manner in which the 

 chromosomes split and separate toward their respective poles is to 

 all appearances identical with the process as described in the di- 

 vision of the central cell nucleus. Fig. 106 represents the telo- 

 phase of this division. The chromosomes have drawn together at 

 the poles, and nuclear membranes are about to be formed. By 

 this time the membrane of the fusion nucleus itself has disappeared, 

 although the nuclear cavity still remains clearly delineated, while 

 the connecting übers are still visible between the massed chro- 

 mosomes. After the development of membranes about the two 



