12 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



ready for division, a weei later tetrads are formed; some- 

 times, however, two cells only result from this division. 

 During the last week of the month the balloon-like 

 appendages become well advanced, and a little later the 

 spores leave the mother-cell. About the second \vet3k in 

 May the spore divides, the resulting nuclei are apparently 

 alike, but the cells formed are very different, for 

 immediately after division the cell towards the rounded 

 end of the spore begins to disintegrate, and speedily 

 becomes a flattened mass against the wall ; the large cell 

 divides a second time, and again one of the resulting cells 

 at once breaks down and becomes flattened upon the other. 



Coulter and Chamberlain regard it " reasonable to 

 suppose that these two evanescent cells represent a 

 vestige of the vegetative tissue of the gametophyte, and 

 that they may be called properly vegetative cells." 



A third division follows, again cutting the spore into 

 two unequal sized cells, the smaller of the two — lenticular 

 in shape — lying immediately below those previously cut 

 off, this is the generative cell, the forerunner of the 

 sperms ; the larger of the two is the tube cell. The pollen 

 grains are now ready for distribution. 



On the first bright sunny day at the end of May the 

 sporophylls open, and should there be the slightest breeze 

 the mature pollen is discharged in great profusion. The 

 buoyancy given to the grains by the balloon-like 

 appendages enables them to be carried hither and thither 

 by the slightest movement of the air. As with all 

 anemophilous plants, the bulk of the pollen is scattered 

 to waste, a small proportion only finding its way to the 

 open scales of the female cones. 



Cell division and the growth of the megasporangia 

 are renewed in the following spring, generally during the 

 last week in March. Growth is rapid, for early in the 



