such mechanism in a race of xerophytic arboreal organism ; and the cone in its final 

 stages of elaboration becomes, in fact, the distinctive feature of the group, playing 

 a part in the biology of reproductive processes quite on a par with the ' ovary ' 

 specialization of the Angiosperm, and hence undoubtedly contributing to the present 

 success of the race in maintaining a footing in the world, which otherwise has largely 

 passed over to the domination of the Dicotyledonous ' Flowering Plant '. 



Fundamentally a collection of leaf-members in a phyllotaxis system, the further 

 organization follows the phyllotaxis-sequence, whether spiral (Fibonacci) or whorled 

 (Cupressineae), of the photosynthetic vegetative shoots. The number of units, 

 originally as ' indefinite ' as in the microstrobilus, and possibly several hundreds 

 (600 in Araucaria brasiliensis, over 200 in Pinus Coulteri), ranges from over 100 

 in most species of Pinus, Picea excelsa, Cedrus Libani, &c., to a few score, of which 

 many may again be sterile at both ends of the system (Pinus edulis, Sequoia], and 

 attains a limit of 4, 3, and 2 scales, which may alone be ' fertile' (Callitris, Cupressus 

 Nootkatensis, 4 ; Juniperus communis, 3 ; Libocednis, 2). 



The essential departure is seen in the great increase in volume of the component 

 units following the necessity for the protection of the enlarging prothallial stages, and 

 a new series of growth-phenomena is required in the individual carpels. A comparably 

 similar phenomenon obtains in the evolution of the fruiting carpel of the Angiosperm 

 (cf. Pea-pod), and the new problems are solved along very similar lines; though 

 subsequent to fertilization in the Angiosperm instead of before it as in Pinus. 



If the carpellary scales are to maintain the same space-relations, and continue to 

 subtend the same angle at the surface, an active rate of growth will be required, the 

 greater at the periphery (Cupressus\ to relatively massive facets. Where such growth 

 is wanting, the scales must open out and make new contact-relations at the surface 

 (Araiicaria imbricata, A. brasiliensis). Bearing in mind the fact that the carpellary 

 scales are themselves vestigial, and wholly decadent, the possibility of their rising to 

 the occasion appears somewhat remote. As a fact of observation the actual cone- 

 mechanism, in the most successful types, has been gradually transferred to a wholly 

 new growth initiated in response to the necessity for the effective sealing of the cone. 

 Since the new growths are thus associated with the original scales and their ovules, the 

 same phyllotaxis-constants may be retained, and the new growths may attain the 

 massive formation required in order to subtend the original angle, giving greatly 

 enlarged cone-facets at the surface. 



So important does their mechanism become, as the characteristic solution of this 

 special problem, that its precocious development follows naturally as an inevitable 

 consequence ; and, in the limit, the secondary growth of the ' cone-scale ' replaces the 

 vestigial carpels, even in the floral mechanism of ovule-protection and pollen-collection, 

 appearing in development as soon as the ovules themselves, and imitating by a slender 

 pointed ' mucro ' (Pinus only) the vestigial lamina of the original megasporophyll. 



Note. In very similar fashion the secondary syncarpous ovuliferous region of an 

 Angiosperm is precociously formed in the flowering period ; the original carpels 

 being wholly lost (cf. Cruciferae), or retained solely for pollen-collection (cf. 

 Compositae). The essential difference between these so-called Gymnosperms and 

 the Angiosperms, in this respect, may be traced to the fact that in the former 

 (as in Selaginella and contra Cycads) the carpels appear to have lost the ovuliferous 

 function before the demand for this new extension was felt, while the Angiosperm 

 prototypes with foliaceous and ovuliferous megasporophylls more in the manner of 

 Cycas, retained, at least in many cases, a capacity for the formation of a closed 

 chamber (apocarpous or syncarpous) in varying degrees; the extreme precocity 

 of which in floral mechanism, sealing the chamber before pollination, involved the 

 elaboration of a ' stigmatic ' surface. It is, again, interesting to compare the 

 ' syncarpous ' extension found in Juniperus, but only produced after initial and normal 

 gymnospermic pollination. Thus the case of Juniperus illustrates one method of 

 initiating a syncarpous ovary-chamber, giving an indehiscent fruit for bird-dispersal, 

 without necessary progression via a condition of ovuliferous apocarpous carpels; 

 a similar result being attainable by different routes ^convergence'}. While it is 



1 As in the case of the Angiosperm ovary and fruit, such constructions, involving the extensive 

 utilization of basal intercalations, can be only understood by following the growth throughout the 

 season, on a series of sectional drawings planned to the same scale. 



II A 3 



