K. M iy ak e , Contribut. to the Fertiliz. and Embryogenj' ot Abies balsamea. 139 



formed before tlie sperm - niicleus approaches the egg-nucleus as 

 observed by Ikeno ('98) in Cycas remains to be determined. After 

 the sperm -nucleus comes into contact with the eg-g--nucleiis it partly 

 imbeds itself mto the substance of the latter, its wall still being- 

 intact (Fig-. 33). The egg-nucleus figiired in Fig. 33 stained diffusely 

 by taldng very little stain, and might be interpreted as represeuting 

 a disintegrating stage as siiggested by Miss Ferguson. The pro- 

 cess of conjugation, however, seems to be normal. I Avas not able 

 to observe the later stages of the conjugating nuclei. The process 

 seems to be, on the whole. similar to those already studied in the 

 other members of the Abietinae. Cavara ('00) observed the conju- 

 gation of the sexual nuclei in Ahies pectinata, and stated that the 

 fusion of the two nuclei takes place in the prophase or in the be- 

 ginning of the spireme stage. The fertilized nucleus soon divides 

 into two equal nuclei (Figs. 34 — 35). The two nuclei increase in 

 size and soon divide simultaneously to form four nuclei of equal 

 size (Fig. 36, 43 a). When the four nuclei have attained theii' füll 

 size, they move down to the base of the archegonium and arrange 

 themselves in one plane (Fig. 37). The basal nuclei then divide 

 simultaneously in a plane transverse to the longer axis of the arche- 

 gonium (Fig. 38, 39). After the division is completed and the eight 

 nuclei are thus formed, walls are laid down between them, but not 

 above the upper four nuclei. Thus a tier of four completely walled 

 cells are cut oif below, and the upper tier remains incomplete, bemg 

 Ireely exposed above to the main mass of the egg-cytoplasm 

 (Fig. 40). The next two divisions in the formation of the proembryo 

 have not been observed. The proembryo when completed consists 

 of four tiers of cells of four cells each, the upper tier being incom- 

 plete since the nuclei are separated from one another by walls but 

 freely exposed above to the egg-cyptoplasm. 



The fate of the second sperm-nucleus, the tube- 

 nucleus and the stalk-cell. 



The Contents of the pollen-tube discharged into the %gg remains 

 in the upper part of the Q,gg^ except the first sperm-nucleus which 

 moves down to the egg-nucleus. The rest disintegrates and flnally 

 becomes mixed with the egg-cytoplasm. The nuclei before disintegra- 

 ting seera to divide, or at least to present ligures more or less like 

 those of mitotic division. Two or three such nuclear ligures are often 

 found in the upper part of the egg at the two or fom* segmentation- 

 nuclei stage. One such egg is shown in Fig. 43. A little below 

 the centre of the egg is a karyokinetic tigm-e represeuting the second 

 division of the fertilized nucleus, whil in the uppei* part one nucleus 

 and three nuclear figures are seen. Two of these hgures on the 

 right hand side which are shown more magiiified in Fig. 43b are 

 connected by a narrow area, as in the dividing two segmentation- 

 nuclei, and seem to represent the second division of the second 

 sperm-nucleus. The smaller flgure on the left side may represent 

 the nuclear figure of, either the te tube- nucleus or the nucleus of 

 the stalk-cell. The nucleus in the uppermost part of the egg may 

 either be derived from the tube-nucleus or the nucleus of the ventral 

 canal-cell. 



