366 GENERAL MORPHOLOGY OF PLANTS 



len tube makes its way into the neck end of an egg case, 

 and empties the cells and sperms into the cytoplasm of the egg 

 (% 359)- The larger sperm (which was in 

 advance in the pollen tube) unites with the egg 

 30 nucleus, and without any resting stage the fer- 

 tilized egg nucleus at once divides into two, and 

 these into two more. These four nuclei move 

 to the base of the egg case, and there by suc- 

 cessive divisions organize the embryo, which is 

 Pine seed, section pushed down into the mass of the endosperm by 



of. sc, seed coat; n, , r ., n . ., 1-11 



remains of nuceijus; certain or its cells in the rear, which elongate 

 female gam<5ophyte7; rapidly and are called the suspensor. The seed 



emb, embryo = young -\ . -, . , r ,, , 



sporophyte. Seed co.it ripens in late summer and consists of the seed 



sporo- coats (coats of the ovule), the remnants of the 

 nucellus, the endosperm and embryo with its 

 rudimentary root, stem and leaves. In the germination of the 

 seed (paragraph 13) and establishment of the young pine plant 

 the life history is completed. 



OTHER GYMNOSPERMS.* 



531. The Cycads. The other most prominent class of the 

 Gymnosperms is made up of the cycads (order Cycadales) . These 

 are mostly tropical or subtropical plants, but some are often 

 grown in greenhouses, especially the Cycas revoluta, sometimes 

 incorrectly called sago palm f on account of its trunk and large 

 spreading leaves at the apex, giving it the aspect of the tree palms, 

 and because of a coarse starchy material obtained from the stem 

 called Japanese sago. Some of the cycads like Zamia (there are 

 several species in Florida) have tuberous-like trunks. The leaves 

 are large, stiff and feather-like because of their narrow, pinnate 

 divisions, and resemble the leaves of some of the tree ferns. In 

 their fructification they bear a striking resemblance to the ferns, 

 and stand lower in grade of classification than the conifers. 



* For special assignment or reference. 



f The sago palm is Metroxylon Icevis and M. rumphii of the East Indies 

 (Chapter XXXVI). 



