10 GENUS PINTS 



THE APOPHYSIS. 



The apophysis represents the later and larger growth of the cone-scale. With a terminal umbo the 

 margin of the apophysis is free and may be rounded (fig. 49) or may taper to a blunt point (fig. 52), 

 and any extension of the scale is a terminal extension. With the dorsal umbo all sides of the apophy- 

 sis are confined between other apophyses, and any extension is a dorsal thickening of the apophysis 

 or a dorsal protuberance. The outline of an apophysis with a dorsal umbo is quadrangular, or it is 

 irregularly pentagonal or hexagonal, the different forms depending on the arrangement of the con- 

 tiguous scales, whether of definite or indefinite phyllotactic order, a distinction to be considered 

 later. 



The two positions of the umbo result from the relative growth of the dorsal and ventral surfaces 

 of the cone-scale. With the terminal umbo the growth of both surfaces is uniform, with the dorsal 

 umbo the growth is unequal. A true terminal umbo rests on the surface of the underlying scale, al- 

 though several species with terminal umbos show the first stages of the dorsal umbo. The umbo of 

 P. Lambertiana or of P. flexilis does not touch the surface of the scale below, and a small portion 

 of the under side of the apophysis is brought into view on the closed cone. The cone of P. albi- 

 caulis (Plate VIII, fig. 90) shows all degrees of development between a terminal umbo near the apex 

 of the cone and a dorsal umbo near its base. 



The growth of the apophysis may be limited and constant (strobus, echinata, etc.) or exceedingly 

 variable, ranging from a slight thickness to a long protuberance (pseudostrobus, montana, etc.) . 

 The protuberance is usually reflexed from the unequal growth of the two surfaces. With the terminal 

 umbo the protuberance lengthens the scale, with the dorsal umbo it thickens the scale. It is some- 

 times a specific character (ayacahuite, longifolia) appearing on all cones of the species, sometimes 

 a varietal form, associated in the same species with an unprolonged apophysis (sylvestris, montana). 



On different parts of the same cone, base, centre or apex, the dimensions of the apophyses differ, 

 but at each level the scales may be uniform on all sides of the cone. That is to say, the cone is sym- 

 metrical with reference to any plane passing through its axis. This, the symmetrical cone, is charac- 

 teristic of all other genera of the Abietineae, and is invariable among the Soft Pines and in many Hard 

 Pines (figs. 47, 48, 52, 54). But among the Hard Pines there is gradually developed a new form of 

 cone with smaller flatter apophyses on the anterior, and larger thicker apophyses on the posterior 

 surface. This is the peculiar oblique cone of Pinus (figs. 50, 51, 53), symmetrical with reference to 

 one plane only, which includes the axis of both cone and branch. The oblique cone is a gradual devel- 

 opment among the Hard Pines ; in some species it is associated as a varietal form with the symmetri- 

 cal cone, and finally, in some serotinous species, it is the constant form. 



THE OBLIQUE CONE. 



When the oblique cone is merely a varietal form (halepensis, etc.), it gives the impression of an 

 accident, resulting from the reflexed position of the cone and the consequent greater development 

 of the scales receiving a greater amount of light and air. But with the serotinous cones (radiata, 

 attenuata), the advantages of this form become apparent. The cones of these species are in crowded 

 nodal clusters, reflexed against the branch (fig. 50). The inner, anterior scales are perfectly pro- 

 tected by their position, while the outer, posterior scales are exposed to the weather. These last only 

 are very thick; that is to say, there is an economical distribution of protective tissue, with the great- 

 est amount where it is most needed. The oblique form is peculiarly adapted for a cone destined to 

 remain on the tree for twenty years or more and to preserve its seeds unimpaired. Like the 

 persistent cone, the oblique cone finds in association with the serotinous cone a definite reason for 

 existence. 



