3o6 



MOKPHOLOGY. 



gates 1)V the formation of a tul><"*, forminf^ a sac, known ns the [xillen lulje 

 It is either simple or l)ranrhed. It grows down into ihe tissue c)f the nu 

 cellus, and at a stage represented in fig. y-^'^, winter overtakes it and il 

 rests. At this time the central cell has divided int(j two cells, and the 

 vegetative nucleus is in the pollen tube. 



622. The endoBperm. — In the following spring growth of all these parts 



Fip:- 3 5 0. 

 Section of nucelUis and eml' jspcrin i if wliite pine. The inner la>'cr of cells of 

 the integument shnwn just outside (it nucellus; anh, arelK'K"nium ; r??, egg- nu- 

 cleus. In the nucellar cap are showii three pollen tubes, vn, veg'etati\'e nucleus 

 or tube nucleus; sU\ stalk cell; spii, sperni nuclei, the larger one in ad^'ance is 

 the one whicli unity's with the eg^ nucleus. Tlic archcgnnia are in the endosperm 

 or female j;ametMph\i<.'. (After Ferguson.) 



continues. The nui lei in llic inai rospori' di\ide to form more, and event- 

 ually cell walls arc formed between them making a distinct tissue, known 



