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



and it will readily be seen that there is considerable diversity in 

 their relative size. Noren (1907) states that in the European 

 form the two are nearly equal, and, as figs. 97 — 99 show, this is 

 often the case, but it is by no means the rule. The Volumetrie 

 ratio, for example, of the nuclei represented in flg. 100 is about 

 4 : 1. The mass of cytoplasm and starch derived from the male 

 cell (indicated in the smaller figures by the dotted line) gradually 

 surrounds the conjugating nuclei, so that there is never any possi- 

 bility of mistaking the fusion nucleus for an unfertilized egg nucleus. 

 After the union the fusion nucleus gradually migrates toward the 

 base of the egg. 



The two nuclei apparently fuse while in a resting condition 

 (fig. 102). Previous to the dissolution of the membranes between 

 them there sometimes appears to be a condensation of the sub- 

 stance of the male nucleus near the surface of contact, but, although 

 more than thirty archegonia were examined which showed the 

 male and female nuclei in contact with one another, in none of 

 them was there any indication that the spirems of the first seg- 

 mentation division are formed before the dissolution of the dividing 

 membranes, as is the case in Pinus (Ferguson 1904). A still 

 larger number of conjugating nuclei were found in which fusion 

 had taken place, yet in none of these was the writer able to 

 distinguish the male from the female elements until the Organization 

 of the definite spirems just previous to the first segmentation 

 division. 



The nucleus of the fertilized egg presents various appearances 

 which, in the light of present knowledge, it is impossible to inter- 

 pret satisfactorily. Noren's figures (1904, fig. 4; 1907, figs. 76, 77) 

 show the strueture very well, so far as it can be made out. As 

 a rule a faintly staining network is visible, but sometimes the 

 entire content of the nucleus, with the exception of the various 

 nucleolus-like bodies, appears almost homogeneous. The most con- 

 spieuous struetures are the nucleoli and pseudonucleoli which are 

 usually indistinguishable from one another. These may be bunched 

 together or distributed through the nucleus; they may appear in- 

 timately connected with the reticulum or entirely disassociated 

 from it; and their affinity f or stains also varies greatly, — in some 

 cases all stain deeply with iron-haematoxylin, while again some 

 stain scarcely at all. 



Development of the proembryo. — Blackman (1898) 

 observes that in the fusion nucleus of Pinus "the chromosomes of 

 the male and female nuclei could be distinguished into two groups 

 at the time when the first segmentation spindle was in the multi- 

 polar condition", while Chamberlain (1899), working indepen- 

 dently, reports the presence within the oospore nucleus in this 

 genus of two distinet spirems. The results of these two writers 

 are amply confirmed by the extensive investigations of Miss Fer- 

 guson (1904), while Woycicki (1899) and Murrill (1900) find 

 similar phenomena in Larix and Tsuga respectively. Under such 

 conditions, as Blackman points out, the process of fertilization 



