II. SYSTEMATIC. 



This is one of the largest of Austrahan pines, attaining sometimes a height 

 of 200 feet. The bark is characteristic, having the appearance of horizontal 

 bands ^hence the name Hoop Pine\ and is hard, compact, and permeated with 

 oleo-resin cells. Leaves are dimorphic, being crowded, spirally arranged, imbricate, 

 incurved, 3 to 4 lines long, ribbed, pungent pointed, in one case, and on tlie lower 

 branches spreading, straight, vertical, decurrent, and sometimes over an inch 

 long. Male amentum sessile, cylindrical, compact, 2 to 3 inches lon^^, about 4 lines 

 in diameter ; the scale-like apices of the stamens are ovate-rhomboidal and acute. 



Fruit cones ovoid, about 4 inches long and 3 inches in diameter, the scales 

 broadly cuneate, the original sporophyll apex developing into a recurved, rigid, 

 acute point. 



III. LEAVES. 

 (fl) Economic (none appears to be known). 



(b) Anatomy. 



These are of a dimorphic character, both forms of leaves being inserted on 

 the branchlets in a spiral arrangement. 



The vertically flattened form of leaf is generally found on branchlets growing 

 from the main stem, and in the shade of the whole tree foliage. It is spread- 

 ing, slightly oblitjue, pungent pointed, and gradually widening all the way to 

 the base, which is attached vertically to the branchlet, slightly decurrent, and 

 measures under an inch long. Most probably the disposition of this leaf accounts 

 for its morphological difference from the normal one. 



A cross section (Figure 229), wliich is rhomboidal in shape with ilir two 

 shorter sides on the upper surface, shows perhaps a greater unifonnilN- of leaf 

 structure than holds in the Callitris, for a single row of epidermal cells extends 

 around the whole, and these are subtended by a single row of hypodermal cells, 

 which in turn are suix-rimjjosed upon a single layer of palisade parenchyma, which 

 cells perhaps are more numerous towards the u])i)er surface. The fundamental 

 tissue — the spongy mesophyll, forms a very large proportion of the leaf substance, 

 and is composed of exceedingly tliin-wallcd, elongated, irregularly-shaped cells, 

 much differentiated from the i^alisade parenchyma and Ncrv little rescinhliiiL; the 

 spongy tissue of ordinary mesoi)hyll. 



There is only one bundle, which is normally orientated, and situated in the 

 centre of the leaf substance, with a protective sheath of endodermal parenchy- 

 matous cells. A few sclerenchvmatous hbres are found on the outer edge of the 

 phloem (Figure 230). 



