CHAPTER IX 
SEED PLANTS (SPERMATOPHYTA) (@YMNOSPERM 2) 
One of the most notable peculiarities of the higher 
Pteridophytes is the extreme reduction of the gameto- 
phyte and the corresponding specialization of the 
sporophyte. This culminates in the various hetero- 
sporous types, where the gametophyte may lack all 
power of independent growth and serve merely to de- 
velop the reproductive organs and nourish the embryo- 
sporophyte until it is,self-supporting. In Selaginella 
the gametophyte is partially developed within the 
spores while they are still included within the sporan- 
gium, and is nourished directly from the sporophyte 
through the sporangium wall, which serves thus not 
only to protect the spores, but also to nourish them 
during the early stages of germination. Finally, how- 
ever, the spores are discharged from the sporangium, 
and the gametophyte completes its development away 
from the sporophyte. 
In the highest of all plants, the seed-bearing, or, 
as they are commonly called, the “flowering plants,” 
heterospory is carried one step further, and the macro- 
spore remains permanently within the sporangium. Not 
only is the germination of the spore completed within the 
sporangium, but the fertilization of the archegonium is 
effected and the development of the embryo-sporophyte 
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