FORM-FACTORS IN CONIFERAE 



DURING the last decades the investigation of Gymnosperms, and more particularly 

 that of Coniferous trees, has been concerned with the detailed examination of repro- 

 ductive processes and phases, as also of cytological phenomena, with a view to deter- 

 mining ' affinities ' by the more obscure relations of the vestigial gametophytes and 

 sexual organs. 1 Anatomy and timber-structure have been more intensively studied, 2 

 but the general external morphology remains very much in the state it was left at the 

 hands of an older generation. 3 Much can, however, still be done in the observation 

 of the more striking characters as seen with the naked eye ; there being many such 

 features which appeal to an observer in the open, though they may be less appreciated 

 in the laboratory. Many of the older generalizations, again, are capable of revision in 

 the light of a broader modern outlook on the general problems of ecology and biology 

 of the vegetable kingdom as a whole. 



Such broader features of growth-form cover a wide range of morphological 

 adaptations as representing solutions of special biological problems, of a significance 

 quite as important in the everyday life of the organism as the more minute mechanism 

 of cell-anatomy, or of racial continuation, and may be equally archaic and vestigial in 

 some respects, as presenting the progression of a unique and disappearing race of 

 tree-forms. 4 



Somatic Organization, including specialization of the space-form of the plant, 

 and its adaptation to subserve different functions, involves the successful utilization of 

 a few simple general factors of the relation of 'stem' (axis] and 'leaf (appendage or 

 'member'). This conventional standpoint is very generally accepted as a postulate 

 for the study of subaerial vegetation, but has been deduced solely from the academic 

 contemplation of the land-plant. Yet even these fundamental conceptions are to be 

 traced back to submarine ancestry, as somatic adaptations for existence in a medium 

 very distinct from that in which such plants are now found, and are to be explained 

 as part of the inherited equipment of the race, established in response to an entirely 

 different system of physical factors, but now ingrained as an unalterable constant 

 feature of the organization ; just as in the case of the dorsiventral human body with 

 axis and limbs, for which an origin must be sought in the fish of ancient seas. 



I. Phyllotaxis: The leaf-arrangement of Conifers is normally based on a 

 Fibonnacci construction (< ratio) ; i. e. the leaf-system at the growing-point shows in 

 its first visible inception contact-curves in terms of the numbers 3, 5, 8, 13, &c. 

 (Abietineae, Taxodineae, Araucarineae), with few minor exceptions ; this spiral 

 arrangement being remarkably constant and accurate. Relics of the pattern may be 

 long expressed on the surface of older axes, as they are also familiar in the fruiting 

 cones ; while these primary relations of the leaf-primordia control the subsequent 

 arrangement of the branches of the main stem. 



1 Saxton (1913), p. 242 ; Sevvard (1919), p. 106. 



3 Penhallow (10.07). 3 Masters (1891). 



4 The most majestic productions of the vegetable kingdom are rapidly disappearing, and will 

 never be replaced. No future scheme of forest-cultivation will even countenance a tree growing to 

 maturity in 500-1,000 years, and persisting for 3,000-4,000. The records of an older generation are 

 already often regarded with scepticism ; cf. American data (Sargent) ; Pinus Lambertiana, 245 ft. 

 and 1 8 it. diam. (Douglas) ; Weymouth Pine of Eastern States (P. Strobus], 250 ft. and 6 ft. diam. ; 

 Sitka Spruce (1806), 300 ft. and 13 ft. diam. ; Sequoia seinpet-virens, 400 ft. (Sargent) ; S. gigantea; 

 35 ft. diam., and 4,000 years old, giving 50,000 c. ft. of timber ; Douglas Fir, 350 ft. and 16 ft. diam., 

 Abies grandis, 300 ft. 



The same applies to the Kauri Pine of New Zealand, recorded at 275 ft. and 22-24 ft- diam. (Kirk), 

 with cylindrical bole 100 ft. and estimated yield of 30,000 c. ft. of timber (Hutchins). Modern 

 forestry prefers a tree of 2 ft. diam. in 100 years. 



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