The cones of Hard Pines, by reason of relatively more and smaller scales and of a more conical form, attain a higher phyllotaxis and a more complex condition, two or even three orders being represented on a single cone; while the cones of Soft Pines, by reason of relatively fewer and larger scales and a more cylindrical form, are of lower phyllotaxis, with one order only more or less definitely presented. Therefore phyllotaxis furnishes another distinction between the two sections of the genus, but its further employment is exceedingly restricted on account of the constant repetition of the same orders among the species. [Illustration: PLATE V. PHYLLOTAXIS OF THE CONE] THE CONE-TISSUES. Plate VI. The axis of the cone is a woody shell, enclosing a wide pith and covered by a thick cortex traversed by resin-ducts. By removing the scales and cortex from the axis (fig. 65) the wood is seen to be in sinuous strands uniting above and below fusiform openings, the points of insertion of the cone-scales. From the wood, at each insertion, three stout strands enter the scale, dividing and subdividing into smaller tapering strands whose delicate tips converge toward the umbo. Fig. 70 represents a magnified cross-section of half the cone-scale of P. Greggii; at (a) is a compact dorsal plate of bast cells; at (e) is a ventral plate of the same tissue but of less amount; at (b) is the softer brown tissue enclosing the wood-strands (d, d) (the last much more magnified in fig. 69) and the resin-ducts (e, e). WOOD STRANDS. The wood-strands, forming the axis of the cone, differ in tenacity in the two sections of the genus. Those of the Soft Pines are easily pulled apart by the fingers, those of the Hard Pines are tougher in various degrees and cannot be torn apart without the aid of a tool. This difference is correlated with differences in other tissues, all of them combining in a gradual change from a cone of soft yielding texture to one of great hardness and durability. If a cone scale of P. ayacahuite is stripped of its brown and bast tissues (fig. 66) and is immersed in water and subsequently dried, there is at first a flexion toward the cone-axis (fig. 67) and then away from it (fig. 68). The wood-strands are hygroscopic and coöperate with the bast tissues in opening and closing the cone. This appears to be true of all species excepting the three species of the Cembrae, whose strands are so small and weak that they are not obviously affected by hygrometric changes. BAST TISSUE. With the exception of the three species of the Cembrae the inner part of the cone-scales is protected by sclerenchymatous cells forming hard dorsal and ventral plates (fig. 70, a, c). In Soft Pines these cells are subordinate to the more numerous parenchymatous cells, but in Hard Pines the sclerenchyma increases in amount until, among the serotinous species, it is the predominating tissue of the cone-scale, giving to these cones their remarkable strength and durability.