92 



Figure 42. — Transverse section through a branchlet and leaves, with 

 one smdioil cavity in one of the leaves. C. robusla, x 70. 



continuous with them, are closely packed round the central column at the 

 lower part of this concavit}', probably to counteract the absence of other protec- 



ti^•e media such as epidermal 

 and hypodermal cells and pali- 

 sade tissue in this part. 



The central vascular cylinder 

 (branchlet) is single, or branched 

 by medullary pith cells, whilst a 

 branch bundle is present in the 

 inner portion of the leaf. 



Endodermal cells occur and 

 surround, when present, the oil 

 gland and cells of the con- 

 junctive or transfusion tissue 

 (which latter is here found in 

 greater proportion than in other 

 species), as well as the phloem of the central axis. 



It is interesting to note how in that part of the leaves where no oil gland is 

 present, the cells which eventually become endodermal are clustered in the centre 



of the spongy mesophyll ; and 



as the oil gland develops, it 

 pushes through the centre of 

 these, which then extend and 

 surround it, the transfusion 

 tissue, and the leaf bundle. 



Figure 42 is a transverse 

 section through a branchlet and 

 the three decurrent leaves, just 

 below the location of the oil 

 cavity, or at least only just 

 sufficient to cut the base of one 



Figure 43. 



-Transverse section throu^:' i t in lil-'I ami (hrciirr^-rit 



leaves, showing an oil cavity in iwu uf llw h-aves, bi-low 

 which is a bundle. The dark c<'ll content in tin pith rays 

 and at the base of the decurre[it channel is probably a 

 manganese compound. C. rohusia, x 70. 



as shown in top of the right sec- 

 tion. Figure 43 is a cross sec- 

 tion higher up than Figure 42. 

 In this case the knife passed 

 through the oil glands, i.e., the circular spaces in the two lower leaves. In the 

 centre of the top leaf is a cluster of Ihin-walled parenchymatous cells, which are 

 gradually displaced or pushed aside as the oil cavity develops, and in the two 

 lower leaves they can be noted arranged around the oil cavity between which and 

 the central axis is the leaf bundle. The elongated or conical cuticle cells of the 

 transpiratory surfaces can be seen, and a guard to which is formed by the incurved 



