30 
PHARMACEUTICAL BOTANY 
Seed Formation and Distribution.- — The oospore undergoes re- 
peated divisions and forms the embryo or young sporophyte plant 
and a suspensor to which it is attached. The embryo is nourished 
by a portion of the prothallus but the greater part of the prothallus 
forms the endosperm tissue of the seed surrounding the embryo. 
The thin nucellus persists as an endosperm covering. The integu- 
ment becomes modified to form the hard protective seed coat. A 
Fig. 12. — White pine (Pinus Strobus). Vertical section through theupper part 
of an ovule, shortly before fertilization, s.n., sperm- nuclei; st. c., stalk-cell; t.n. 
tube-nucleus; arch, archegonium; e.n., egg-nucleus. (Gager, after Margaret C. 
Ferguson.) 
portion of the scale of the cone directly above and adjacent to the 
ovule forms a membranous wing which separates from the scale as 
part of the seed. 
By this time (about two years after pollination) the scales of the 
cone, now quite woody, separate, the seeds are shaken out, and many 
are carried for a considerable distance by winds. 
