CHAPTER XVIII 
SPERMATOPHYTES (SEED PLANTS) 
Gymnosperms (seed not enclosed) 
Spermatophytes or Seed Plants constitute the fourth large 
division of plants. They are the most highly developed plants, 
and, therefore, in them we find the final achievement of plant 
evolution. Their distinguishing feature is the seed, although 
they have other notable features not found in the groups pre- 
viously studied. The notable features of Pteridophytes, such as 
sporophylls, strobili, heterospory, dependent gametophytes that 
are developed within the spore wall, and the retention of the 
megaspore in the megasporangium, are retained by the Sperma- 
tophytes and to these they have added new features. Because 
of the seed, lumber, fibers, and numerous other products ob- 
tained from them, the Spermatophytes surpass all other divisions 
of plants in economic importance. They are also very numerous, 
and on account of the large size of their sporophytes they are our 
most conspicuous plants. 
The Spermatophytes are divided into two groups, — the Gym- 
nosperms and Angiosperms. As the names suggest, the Gym- 
nosperms bear their seeds exposed while Angiosperms bear them 
enclosed, but the two groups differ also in other features as will 
be noted later. 
The Gymnosperms are more primitive than the Angiosperms 
and are, therefore, more like the Pteridophytes, the group from 
which Seed Plants are supposed to have originated. The groups 
of Gymnosperms most like Pteridophytes are now extinct and 
hence are known only by their fossils. Some of these extinct 
forms resembled Ferns so much that they are called Pterido- 
sperms, a term which means “ Ferns with seeds.”” Thus Gymno- 
sperms connect more closely with the Pteridophytes than the 
latter group does with the Bryophytes. The Gymnosperms still 
in existence are divided into a number of groups, but a study of 
the Cycads and Pines will give a notion of the general features 
characteristic of Gymnosperms. 
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