THE SPERMATOPHYTES 463 
embryo grows. ‘The hypocotyl, elongating, forces its way out 
through the micropyle and arches downward into the soil, most 
of it becoming the primary or main root. The upper part 
becomes the stem. The cotyledons remain within the seed. 
The epicotyl pushes its way upward and develops the rest of the 
stem, also the green leaves of the seedling sporophyte. As 
Rew ik * 
Fic. 349.—Ginkgo biloba, the Maiden-hair tree. 
soon as the green leaves and the root with its absorbing root hairs 
are developed, the seedling becomes an independent organism 
developing either into a mature male or female sporophyte. 
ORDER GINKGOALES 
The Ginkgoales is represented by the single species, Ginkgo 
biloba, the maidenhair tree, a native of western China and grown 
extensively in China and Japan and the United States as an 
ornamental tree. It possesses a straight trunk from which 
