13 2 MARGARET C. FERGUSON 



nuclei. These bands without doubt represent the separated-out 

 paternal and maternal chromatic substance. This phenomenon 

 is of especial interest in that it suggests a cytological basis for 

 Mendel's laws. A longitudinal splitting of the chromosomes 

 first becomes apparent during an early stage in metakinesis. 



The four segmentation-nuclei attain full size while still in 

 the upper part of the egg. As they pass to the base of the 

 oosphere, fibers occur in the cytoplasm similar to the threads 

 observed around the growing egg-nucleus. The steps in the 

 division of these nuclei have not been carefully traced, but, 

 from the stages observed, it is probable that this mitosis does 

 not differ from the division of the two segmentation-nuclei. 



No cell-wall is laid down at the base of the oosphere until 

 after the eight-celled stage of the proembryo has been reached. 

 These eight nuclei are surrounded by a deeply-staining granu- 

 lar substance which extends out from each nucleus in irregular 

 strands. This substance finally comes to lie in the lines of the 

 future cell-walls and is evidently transformed into cell-wall. 

 It is probably not different from the smaller granules deposited 

 in the line of the cell-plate during the accustomed method of 

 cell-wall formation. 



The fourth division which occurs within the fertilized egg 

 takes place in the four cells of the upper tier of cells at the 

 base of the archegonium. Thus twelve nuclei are formed 

 under the direct influence of the egg-cytoplasm. This fact 

 herein noted for the first time 1 is significant, suggesting as 

 is does a closer relationship with those lower gymnosperms in 

 which many nuclei are formed in the cytoplasm of the egg. 



The number of chromosomes in the nucleus of the ventral 

 canal-cell, in the nuclei of the sheath-cells, and in the egg- 

 nucleus has been found to be twelve, while the mitotic figure, 

 in the first division following fertilization, shows twenty-four 

 chromatic segments. 



It is interesting to note the many points of similarity between 

 fertilization as it has been observed in Pinus, and the processes 

 known to take place during fertilization in some animals, (i) 

 The egg in Pinus is very large and is abundantly supplied with 



1 See note at close of Appendix. 



