SEED PLANTS 



305 



"stem" is really a leaf stalk. The young leaf appears 

 to be rolled up in a spiral, and uncurls as it develops. 

 The leaf is a compound one (cf. 309), 

 with delicate and exquisite veining. 



The reproductive organs of the ferns we 

 ordinarily see are the grain-like spots (sori) 

 on the back of the leaf (Fig. 250). In 

 some ferns, as in the bracken fern, the 

 edge of the leaf is rolled in to protect 

 these organs. 



The leaf "stems" of ferns have woody 

 bundles (cf. 313); hence the leaves are sup- 

 ported easily, even when they grow large 

 and tall. In the tropics there are true ferns 40 feet high. 



(Fruiting Bodies) ' 



327. Seed Plants. Only the seed plants produce 

 true seeds. The oldest seed plants, as the rocks of the 

 earth tell us, were relatives of the pine, spruce, and fir, 



trees which we 

 call evergreens 

 (Fig. 251). In the 

 evergreens, the 

 seed is produced 

 on the carpel, but 

 not in it. Hence 

 these plants are 

 called gymnos- 

 perms (cf. 313), 

 that is, "plants 

 with the seeds 



FIG. 251. Evergreens. In the center a Norway pine. The j , , m -. 



"Christmas trees" are spruce and balsam fir. naKed . i 116 



