20 



THE OAK. 



in the cells of the cotyledons, as do all the parts of the 

 young seedling at this period. In fact, these stores in 



Fio. 8. I. Longitudinal section through the posterior half of the em- 

 bryo, in a plane at right angles to the plane of separation between the 

 cotyledons (slightly magnified). II. Germinating embryo, with one 

 cotyledon removed. III. Acorn in an advanced stage of germination, 

 a, the scar ; #, pericarp ; A, testa ; 5, plumule ; st, petioles of coty- 

 ledons, from between which the plumule, J, emerges ; he, hypocotyl ; 

 c, cotyledons ; /, vascular bundles ; w, radicle (primary root) ; w', sec- 

 ondary roots. Root-hairs are seen covering the latter and the anterior 

 part of the primary root in III. (After Sachs.) 



