THE SEED PRODUCTION OF PIN US SYLVESTRIS. 20 



This cleavage of the egg into sixteen cells — twelve 

 complete and four incomplete' — is very suggestive of the 

 segmentation which takes place in the fertilised eggs of 

 the Metazoa In Pinus sylvestris, however, the segmented 

 egg provides for fonr embryos, and not for one only as in 

 the Metazoa. It is possible that this peculiarity in the 

 genus Pinus has been brought about to provide in some 

 measure against the exigencies to which it has been 

 subjected, exigencies that have compelled it to distribute 

 over a period of three years that which is accomplished by 

 some of its near relatives in the short time of a few weeks. 

 It is just possible that at some time when conditions were 

 more favourable, that only one embryo was provided for by 

 this group of cells. Coulter and Chamberlain have found 

 one example of P. laricio in which but one pro-embryo was 

 proceeding from the group, and these authors state that 

 such seems to be the normal behaviour of Picea excelsa. 



Whatever be the explanation it is a point of curious 

 interest. 



Returning to these cells at the base of the egg : The 

 lower group are destined to initiate four embryos. The 

 next above are to carry the embryos into the midst of the 

 rich food stuffs of the endosperm ; this they do by 

 becoming of great length, occasionally piercing straight 

 into the cell mass below, but more frequently doubling 

 back upon themselves several times. These long cells — 

 suspensors — not only carry the embryo to the abundant 

 food supply, but by reason of the large surface they 

 present absorb it through their walls, and pass it on to 

 their charges. 



I have one example in which the embryos have gone 

 round the adjoining egg, instead of into the endosperm 

 below (fig. 15). 



About a week after the uniting of the gametes the 



