16 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



concentrically arranged tabular cells apparently disin- 

 tegrating ; the inner zone must, I think, be regarded as 

 the equivalent of the tapetal cells of the pteridophytes. 



Although as already noted the pollen grains are 

 deposited upon the nucellus about the end of May, their 

 tubes do not commence growth until a month later — 

 about 1st of July — the time coinciding with the advent of 

 the functional megaspore. The tube nucleus passes 

 immediately into the developing tube, leaving the 

 generative cell still attached to the wall of the pollen 

 grain. By the 1st of August the generative cell has 

 undergone some slight modification, being now nearly 

 globular in shape ; it is about 18 microns in diameter, 

 and its nucleus 8 microns in diameter. In this condition 

 it passes later to its winter rest. 



By the end of July the tubes have grown into the 

 nucellus to a depth of some five or six cells, frequently 

 having given off two or three branches, thus securing safe 

 attachment, and the means of acquiring an ample food 

 supply, these branches acting as haustoria. 



About the same time the megaspore has reached a 

 diameter of about 90 microns, and the spongy tapetal 

 area has extended considerably. 



About mid-October, when the megaspore has reached 

 a diameter of 120 microns, free nuclear division takes 

 place ; at the end of the month the megaspore — now better 

 designated the gametophyte — is 180 microns in diameter, 

 and contains from 16 to 64 free nuclei. Further growth 

 is suspended until the following spring. 



Near the middle of the following March we are at 

 the commencement of the third season, and we enter upon 

 the most interesting portion of this long history. For five 

 and a half months the young cones, with their carefully 

 protected contents, have been subject to the frosts and wet 



