can be no doubt that it represents one of the most critical factors in the history of 

 the race, determining its phyletic progression, as expressed to the present day, in the 

 different horizons of attainment in this particular respect, which characterize the 

 different groups of the Pinoid series. Types of the Cupressineae in which there is 

 no true ' cone-scale ' at all illustrate the primary steps : 



(1) The simplest case is that seen in Thuya gigantea; the enlarging scales are 

 closely adpressed, with considerable basal intercalary extension in the fertile member, 

 taking the tips far beyond the enlarging ovules. A crested growth within the margin 

 of each scale, on the upper surface, establishes adhesion with the next higher scale by 

 means of closely interlocking papillose hairs (100 fj. or more long). This new growth 

 has clearly no connexion whatever with the axillary ovules, but it seals them over very 

 effectually. The growth has no vascular supply, and hence never attains the dignity 

 of a ' cone-scale '. It again clearly suggests the sealing mechanism of the Pinus 

 ovule, as an active extension of the sub-epidermal tissue of the scale over a localized 

 area, and in the mature cone it merely shrivels up. 



(2) In Biota (Thuya orientalis} the original floral segment becomes a massive 

 hook-like process carried up on a succulent extension of the fertile scales which 

 completely overtops the ovules ; the latter are thus quickly submerged and hidden. 

 The margins of the adjacent scale-facets are then sealed by characteristic interlocking 

 papillae of the epidermal cells (5 mm. cone, April). The massive new growth is 

 supplied by a vascular bundle, taking off just above the original one, but presenting 

 inverse orientation (with the xylem on the lower side). This bundle continues to the 

 distal end, but curiously avoids the small sealing protuberance, extending instead into 

 the base of the large hooked scale apex. 1 The succulent tissue contains indefinitely 

 scattered sclerites. 



(3) The same holds essentially for cones of the more generalized Cupressus 

 type (C. Macnabiana, C. Nootkatensis), and close contact of the new scale-facets is 

 similarly assured by interlocking papillae (120 /x) of surface-cells. The floral scales 

 are more insignificant as compared with the new extension, being left as residual 

 spinous processes on the enlarging facets ; and as the sealing extension is relatively 

 more pronounced it is supplied with vascular bundles. In these cases the inverse 

 bundle (or branches from it, C. Macnabiana) passes directly to supply the new- 

 extension on the upper side of the primary one continued to the original scale. 

 Early stages are followed in April (4 mm. cones) and June. The distribution of 

 sclerites is particularly elegant in C. Nootkatensis. 



(4) A variation is seen in Juniperus, in which the basal intercalation of the 

 sealing growth is more emphasized, and the ovules are rapidly submerged (/. sphaenca, 

 2 mm.) ; the general intercalary zone continues to build the berry-like mass, and the 

 original scales close in at the apex by interlocking papillae. In/, communis the basal 

 zone of growth is so emphasized that it may be cut in transverse section as a definite 

 ring of tissue ; the ovules are carried up and appear inserted more on the sides of the 

 new extension ; so that the whole might be fairly described as ' syncarpous with basal 

 placentation ' . 



(5) Cupressus Lawsoniana illustrates a new departure ; the sealing growth on 

 the upper surface of the extending scale is followed by a similar massive extension 

 on the lower side. Corresponding opposed growths meet over the ovules and establish 

 contact by interlocking papillae. It is interesting to note that the basal growth also 

 receives a special bundle-supply (with normal orientation); and this double growth 

 gives the ultimate effect of the so-called peltate (valvate) cone-scales, with the original 

 carpellary unit left in the centre of the facet as a spinous projection (cf. 4 mm. cones, 

 April, 6 mm. cones, June). 



Of these variants the simple sealing-growth of the upper scale-surface or its 

 intercalary basal extension, becomes the normal and more general solution of the 

 problem, to be henceforward emphasized by its precocious formation. Thus in 

 Taxodineae (cf. Cryptomeria japonica) a small crested growth, without V.B., is already 

 in evidence beyond the insertion of the erect axillary ovule at the time of pollination. 

 Subsequently this increases by basal intercalation, overlaps the enlarged ovules, and 



1 Suggesting that the inverse character of this bundle has no necessary association phyletically 

 with the ' cone-scale ' growth. 



14 



