126 



as lysigenous. Under such an irregular disposition of oil cavities no assistance 

 was rendered by these for diagnostic purposes, as obtains in other Conifers, and 

 they cannot be used in a manner employed by Engelmann, who grouped the 

 species of Pinus according to the position of their resin or oil ducts. He also lays 

 stress on the circumstance of the resin canals being surrounded by strengthening 

 cells or devoid of such investment. These conclusions, howe\'er, cannot be 

 applied to Callifn's as far as our observations go. 



Figure 65 is a transverse section, showing the earliest stage of concrescence 

 in the leaf, and where the three divisions are beginning to indi\'idualise, 

 whilst Figures 66-67 show the concrescent portions more distinctly, also the fuller 

 development of the ventral surfaces, and the cuticle protuberances on them. The 

 division of the \-ascular bundles of the central axis into three parts by obtruding 

 medullary pith cells, and the orientation of the phloem (indicated by the 

 darker cells) are well brought out. In Figure 68 the section is interesting in 

 that one or two elongated cuticle projections are seen on the lower part of the 

 assimilating surface. Xo oil cavities occur in this or previous sections, where also 

 the parench\'matous endodermal and transfusion cells are not arranged in any 

 order. The ventral surfaces on the two leaf concrescences have edged together 

 and so shut out any communiciation between the air and the stomata. Figures 69 

 and 70 illustrate the occurrence of an oil cell in the centre of the tissue of each leaf. 

 The parenchymatous cells are here assuming some kind of order of an endodermal 

 nature, and in Figure 70, are clustered around the oil cells, and at the base of the 

 \'entral surfaces. The bundle of each leaf is seen below each oil cavity, the dark 

 patch being the phloem. In Figure 71 the ventral surfaces are shown 

 exposed to the atmosphere, and three well-formed oil cells form distinct objects in 

 each concrescence. The transfusion tissue borders laterally the leaf trace, and 

 extends round towards the oil cavity, and is denoted by the cells with \'ery small 

 pits, which can be seen under a lens. Figure 72 is given to show the 

 unusual occurrence of two oil cells in a concrescence. Figure 73 is a 

 section through the ventral surfaces of two concrescences exposed to the atmos- 

 phere, and two air cavities, and gives the structure in this locality magnified 

 160 times. In Figure 74 the method of protecting the ventral surfaces from the 

 atmosphere by the closing over of the edges of the dorsal surfaces is seen at top 

 of the picture. Figure 75 well illustrates the leaf structure in the locality 

 of the oil cell and leaf bundle; the transfusion tracheids are marked by the 

 bordered pits, and are seen to be irregularly scattered amongst the other cell 

 tissues. On the right is the phloem of the central axis, the .xylem just showing, 

 and to the left is the leaf bum 11'-, tin- jihliirin bring indicated by a black patch, 

 and further removed from this to the left is an oil cavity. 



Figure 76 gives a much finer illustration of the remarks under l*"igure 74. 

 The papillose projections in tlic dccurrcnt (lianiicl an; well maikcd and loi-ni a 



I 



