28 



The histological investigations of the leaf scale, or free portion of the 

 leaf, were discarded for the true leaf, i.e., — that which included the free as well as 

 the decurrent portion, the latter being the leaf proper and upon which the results 

 recorded under each species are founded. 



It was hoped that at least one purpose would be served by investigating 

 the structure of the leaves, viz., that some assistance would be rendered the 

 systematist in the differentiation of species by employing the aid of histological 

 structure, but the results were not quite so fruitful as expected. 



The sections examined showed morphological differences,— the contour of 

 the decurrent portions varying in different species, but these variations were 

 not sufficiently constant for a sj^stematic reliance to be placed upon them in all 

 cases. 



One of the principal features brought to light was that the outer or dorsal 

 surface of the leaf was almost in\-ariabl\- assimilator\-, and that correspondingly 

 the ventral surfaces were transpiratory, — the stomata being arranged along the 

 under surface in the passages formed by the overhanging edges of the concrescence, 

 and onl}' a few were found on the inner surface of the free end at the base, 

 their presence in this position evidently accounting for the incurving of this portion 

 of the leaf as a means of protection. The outer convex surface of the leaves of 

 the interior species may, therefore, be said to be devoid of stomata. Where no 

 decurrent channel exists, the stomata are found on the lateral surfaces below the 

 dorsal ridges, as in the case of the " Weeping Pine." 



One, or rarely more rows of epidermal cells characterise the cuticle, these 

 being superimposed upon single or double rows of hypodermal cells. This again 

 is subtended b}' the mesophyll consisting of palisade cells containing chloro-plastids, 

 followed by loose parenchyma through the centre of which in the upper portion 

 of the leaf is mostly situated an oil cavity or reservoir, fusiform in shape. 



At the point of approach of the two surfaces of the leaf in the concrescent 

 portion, it was found that the cuticle begins to alter in character from that of the 

 dorsal surface, and this changed feature characterises the ventral surfaces, with 

 the exception of one or two species. The cuticle here becomes broken or changes 

 into elongated, conical bodies or papillose projections, whose function is probably 

 to act as secondary guard cells to the stomata. A similar character is recorded 

 and figured by E.G. Bertrand("Ann. des Sc. Nat.," 5e Ser. Bot. Tome, 20., PI. 10) as 

 occurring in the Japanese genus of Conifers, — Sciadopitys. 



The palisade cells are quite absent below the ventral surfaces of tlie inland 

 species, C. glauca. 



The cil cavity or reservoir, supported by secretory cells, is nearly always 

 found in the upper portion of the decurrent section, and between the phloem of 



