2 MARGARET C. FERGUSON 



Chapter II. The male gametophyte. 

 The development of the pollen-grain. 



The formation of the prothallial cells 41 



The mature pollen-grain 44 



Pollination. 



The ovule at the time of pollination 45 



The pollen-chamber 4^ 



Development of the pollen-tube. 

 The first period of growth. 



Germination of the pollen-grain 47 



The division of the antheridial cell 4S 



The winter condition 50 



The second period of growth. 



Renewed activities in the macrosporangium 50 



Renewed activities in the male gametophyte 51 



Division of the generative nucleus 53 



Growth of the sperm-nuclei 62 



Elongation of the pollen-tube 64 



Summary 66 



Chapter III. Macrosporogenesis. 



The female cone. 



The macrosporangium 7° 



Formation of the axial row. 



The macrospore-mother-cell 7' 



The first division of the mother-cell 7- 



The second division of the mother-cell 74 



Significance of the tetrad-division within the ovule 76 



Later history of the axial row. 



The fate of the upper cells 79 



The growth of the macrospore 80 



Summary 81 



Chapter IV. The female gametophyte. 



Development of the prothallium. 



The first period of growth 82 



The second period of growth 84 



The so-called " spongy tissue." 



The first period of growtli 86 



The second period of growth 88 



The nature and functiftn of this tissue 89 



Development of the archegonium. 



The early growth of the archegonium 90 



The division of the central cell 95 



History of the ventral canal-coll 97 



Matination of the egg. 



The descent and growth of the egg-nucleus 99 



Tlie " proteiil vacuoles" 103 



Tlie receptive vacuole 109 



Suinmarv 110 



