I06 THE SCOTTISH BOTANICAL REVIEW 



did not really belong to the embryo-sac. With the exception 

 of the case cited, the antipodal nature of the cells found at 

 the base of the embryo-sac was decidedly doubtful. In most 

 of the specimens examined one large nucleus was found above 

 the base of the sac, and this was found to be the result of the 

 fusion of two nuclei entirely like the formation of the endo- 

 sperm nucleus of the typical embryo-sac. A. pictum, there- 

 fore, differs from A. simplex and A. 7nodestuiii, since in these 

 the two chalazal nuclei do not fuse, but, as we shall see, 

 undergo a second mitosis. 



In fig. 20 there are shown four sections of an embryo-sac 

 of A. simplex in which the two basal nuclei were in process of 

 division. At the apex of the sac was the Q%g apparatus of 

 which the &g^ is shown at c, and one of the synergids at d. 

 The egg has less granular contents than the synergids, but 

 otherwise resembles them. 



The two dividing nuclei were near the middle of the sac, 

 and were surrounded by a considerable amount of finely 

 granular cytoplasm (figs. 21-23). The planes of division in 

 the two nuclei were almost at right angles to each other. 

 The lower nucleus was cut in the median plane of the spindle, 

 which was very distinct. At one pole (fig. 23, x) there was 

 a very conspicuous round body looking like a starch granule 

 or a very large centrosome, but this was absent from the other 

 pole, and probably had no special significance. It is possible 

 that it may have been a nucleolus, though it did not stain 

 very strongly. In the other nucleus (fig. 21) the nucleolus 

 could still be plainly seen. As in the nuclei from the younger 

 sac, the chromosomes were very numerous and quite plainly 

 seen — elongated, somewhat curved rods, — but no satisfactory 

 count could be made of them. 



As the result of these divisions the lower part of the 

 embryo-sac shows four large free nuclei, while at the apex, 

 or at the side of the embryo-sac, is the conspicuous Qgg 

 apparatus. Figs. 26 and 27 show the ^%g apparatus and two 

 of the four free nuclei taken from a series of transverse 

 sections of an ovule of A. simplex. The &%g apparatus is 

 composed of three almost similar cells, but probably the cell 

 0, which has clearer contents than the others, is the ^^g. The 

 free nuclei are large, with a very conspicuous nucleolus, and 



