Fig. 25. —White pine ( Pinus Strobus ). At left, megasporangium with mega¬ 
spore in the center; above, pollen grains in the micropyle and pollen chamber. At 
right, pollen grains beginning to germinate; the cells of the integument have 
X enlarged and closed the micropyh'. (Gager, after Mat garet C. Ferguson.) 
Fig. 26. —White pine (Pinus Strobus). 
of an ovule, shortly before fertilization, 
tube-nucleus; arch, archegonium; e.n., 
Ferguson .) * 
Vertical section through the upper part 
s.n., sperm-nuclei; si. c., stalk-cell; t.n. 
egg-nucleus. (Gager, after Margaret C. 
