Araucaria, with the least differentiation of leaf-members (no bud-scales, no spurs), 

 shows the fewest lateral leaders, with flowering shoots as the only other axillary 

 derivatives ; so far it may be regarded as a very specialized type along its own lines 

 rather than primitive. 



The production of a main leader from a lateral may be effected (Pmus) by the 

 erection of one member (usually the strongest) of the false whorl ; or several may 

 diverge and erect more or less. In the case of Cedrus and Larix, leaders may follow 

 on from a simple spur-growth ; the less so, however, as the spur-growths are older ; 

 and similarly Ginkgo rarely regenerates a new leader from a spur. The case of 

 Araucaria excelsa is of special interest, as a damaged terminal may regenerate 

 a symmetrical terminal growing-point with laterals also symmetrically spaced 

 around it. 



Special foliage-spurs, beginning as shoot-branches with normal leaf-production 

 (Sequoia gigantea), freely cut away from older branches, up to a foot in length, are 

 more emphasized in the deciduous Taxodium distichum, bearing 50 leaves or more, 

 and even branches of higher degree. By omission of internodal extension these 

 reduce to densely tufted or clustered growths, with 3040 leaves per season (Larix} ; 

 reducing further to about 20 leaves per season, for many years in succession (Cedrus}, 

 or about 5 in the deciduous Ginkgo. The number reduces further, 5-3-2, in Pinus- 

 types ; the limit of 2 indicating the highest organization in this respect, as the limiting 

 case of centric symmetry. The case of the single leaf (P. monophytta) is regarded as 

 less satisfactory, and of the nature of a freak ; but a special and equally anomalous 

 case occurs in the ' double needle ' of Sciadopitys, in which the entire sequence of 

 spur-formation has been gone through, attaining a limit of ' false-whorls ' of single 

 ' bifoliar ' spurs in a manner beyond even that of Pinus, and in a distinct alliance. 



Phyllomorphs, also shed as distinct shoot-systems, may be regarded as a special 

 case of spur-formation, on the lines of Taxodium, but branched to the 3rd and 4th 

 degree (Chamaecyparis, Thuya, Libocedrus, Biota). In these last a rhythmic segrega- 

 tion of laterals works out a characteristic pattern, as a ' leaf-mosaic ', the constants for 

 which may vary slightly in the different forms (cf. C. Lawsoniana}. The most 

 interesting feature of the mosaic is possibly the modification of the general scheme in 

 the distribution of the basal ramuli of each degree; a ramification being commonly 

 omitted on the basiscopic side, but put in on the acroscopic flank, giving the effect of 

 3 (2-4) successive ramuli on the front margin (C. Lawsoniana, C. Nootkatensis 3, 

 less commonly 2-4). Similar variations may occur in other forms, 2 (3) successive 

 ramuli in Libocedrus decurrens, 3-4 Thuya occidentalis, 2-5 in Thuya gigantea with 

 more nodal variation, but normal regular alternation in Biota, 



III. Dorsiventrality : For want of a better term it is usual to utilize this 

 expression, borrowed from animal morphology, to express a differentiation of upper 

 and lower surfaces in any bilateral construction, whether of branch-nature or leaf- 

 lamina. The dorsiventral habit in branch-organization is associated with intense 

 insolation and the production of small foliage-members which do not irregularly 

 shade one another. The system as a whole is orientated so that all the leaf-units 

 may obtain a fairly equal light-exposure. As a rule, the more reduced the leaf- 

 member the greater the demand for adjustment in the branch-system as a whole ; 

 so that the latter is treated more and more in the manner of a compound leaf. Thus 

 Ginkgo with broad long-petioled foliage-leaves, more in the manner of ordinary Angio- 

 sperms, presents little branch-dorsiventrality ; the extreme case of such orientation 

 occurs in microphyllous phyllomorphic Cupressineae. 



(a) With the differentiation of an erect leader, maintained vertically by negative 

 geotropism, as a question of balance as well as of optimum exposure to the external 

 medium, the available lateral space is controlled preferably by a symmetrical system 

 of laterals which assume a more or less horizontal position, or ascend at a wide angle 

 (over 45) to be subsequently pulled over by their weight (Araucaria) in graceful 

 curves. Such horizontal projection is also geotropically regulated, to the extent that 

 an individual in which such control is imperfect, so that all the laterals ascend at 

 a steep angle or vertically, is regarded as a monstrosity (fastigiate forms of Cupressus, 

 Taxus, and Spitzfirs Spruce) ; or again if merely pendulous (Serpent Spruce) beyond 

 the effect of normal drooping in a less mechanically efficient axis (leaders of Deodar, 



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