48 Transactions. 



sade form of the parenchyma cells on the upper surface is rather 

 more regular, while the middle cells are narrower and longer 

 on the whole than those of the preceding section. 



In the vascular bundle we find a more clearly defined endo- 

 dermis and a general increase of the conducting elements. In 

 the greater number of the bundles we find a tendency for the 

 bundle to split into two. We find larger transfusion elements 

 at the sides than in the younger cotyledon. 



It is rather interesting to note the complete absence of 

 resin-canals in the cotyledons, especially when in accordance 

 with a prolonged period of growth these leaves have assumed 

 a differentiated character as great or even greater than the 

 succeeding leaves. 



Young Leaf on the same Plant as the Cotyledons, \ in. long. 



The leaf in transverse section presents a long and narrow 

 appearance like the cotyledon, but it differs in having a mid- 

 rib up which runs the single vascular bundle of the leaf. 



The cuticle is thicker again than that of the cotyledon, especi- 

 ally at the margins, and there are also thicker walls around the 

 epidermal cells. 



The stomata here occur only in four longitudinal rows on 

 each side of the vascular bundle, on the lower surface only, and 

 are much more sunk — obvious protections against excessive 

 transpiration. 



The hypoderm occurs as one or two rows at the margins, 

 and extends a considerable way from there in a continuous 

 band round the sides. There is another continuous band above 

 the vascular bundle, while between the margin and the bundle 

 it occurs in irregular groups of two or three. 



The chlorophyll parenchyma presents much the same charac- 

 ters as the cotyledon. 



In the vascular bundle the most striking difference from the 

 cotyledon is the presence of a resin-canal. This is placed in 

 connection with the phloem, and presents the same characters 

 as in other Conifers, secretory cells surrounded by a ring of 

 strengthening cells. The endodermis is better marked, and in 

 the pericycle we find abundant transfusion tracheids showing 

 transitions out from the protoxylem {px), through the centri- 

 fugal tracheids at the sides, to the transfusion tracheids in con- 

 tact with the endodermal cells. The elongated cells of the 

 chlorophyll parenchyma are just outside of the separating 

 endoderm eel's, and hence in direct communication with these 

 tracheids. The phloem has the same character as before, but 

 the crushed protophloem elements do not form so conspicuous 

 a part of the bundle. 



