Ramaley : IIYPOCOTYL AND EPICOTVL IN WOODY PLANTS. 105 



The pith is large-called. A perimedullary zone was not dis- 

 tinguished. 



Cork formation takes place in the second cortical layer as in 

 Cercis siliquastrum (fide Moeller [1882] ). 



Comparison of Structure of Hypocotyl and Epicolyl. 



The epidermal cells of the hypocotyl, when seen in cross 

 section, appear radially, not tan- 

 gentially elongated as in the epi- 

 cotyl. In the former region the 

 endodermis is distinct, the cortex 

 thicker and the sclerenchyma at first 

 differently disposed. 



The stele of the hypocotyl has 

 originally four phloem bundles and 

 four xylem bundles. The young- 

 est material of the epicotyl which 

 was examined has a closed ring 

 of phloem and four large xylem 

 bundles, also a few small groups of 

 xylem. 



Cork formation in the hypocotyl 

 takes place in the lower cortex ; 

 in the epicotyl it takes place in the 

 second cell layer of the cortex. 



Cercis canadensis 

 FlG. 9. 



Gleditsia triacanthos. 

 Structure of Hypocotyl. 



The epidermis is composed of rather thick-walled cells which 

 are oblong in cross section, the long axis being at right angles 

 to the periphery of the section. These cells are eventually 

 elongated in the tangential direction. 



The cortex is very thick. There is no differentiated hypo- 

 derma, but three or four of the outer cortical layers are com- 

 posed of smaller cells than those below. 



The endodermis is definite ; it is large-celled. In some 

 places it is two layers of cells in thickness. Starch, at first 

 present only in the endodermis, is eventually widely distributed 

 throughout all the parenchymatous tissues. 



The stele is cylindrical. There are in the young hypocotyl 



