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DR. If. T. MASTERS ON THE MORPHOLOGY. 































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primordial leaves are different in character from the adult ones 

 while in other species of the same genus, as in A. imbricata and 

 A. brasiliensis, the form of the primordial leaves is practically 

 the same as that of the adult plant (see ante, fig. 3, p. 234). 



In Ginkgo the primordial leaves are tristiehous, alternate, 

 remote, and pass gradually into those of the adult stage (see 

 amU % fig. 1, p. 233). 



In Sciadopitys the primordial leaves are alternate, spreading, 

 long, linear-oblong, and in subsequent stages become reduced to 

 ovate convex scales differing only from perulae in being rather 

 more leafy in character. 



In Pinus the primordial leaves * were recognized by Linnaeus 

 in Pinus Pinea (see fig. 8). They are, so far as known in various 

 species, flat, linear-lanceolate, generally serrulate at the edge 

 (almost exactly as in the leaves of Ly cop odium serrulatum), and 

 arranged as in Sciadopitys. 



In some species, as in P. rigida, P. silvestris, as also in the 

 Douglas fir and doubtless in many others, as a result of injury to 

 the main shoot, the axis commences to branch at the very base 

 just above the cotyledons, and these primary branches produce 

 only primordial leaves. 



When a young shoot branches at the base, so that there are 

 belonging to the same generation a central shoot and a whorl of 

 lateral offsets from it, then it often happens, as in Pinus insignis, 

 that in the quicker-growing and more vigorous central shoot the 

 fasciculate leaves are at once produced, while the side-shoots 

 of weaker growth bear primordial leaves only, without buds or 

 fascicles in their axils. 



Usually it happens that the primordial leaves gradually pass 

 into the position of perula-like scales, or, as they have been called, 

 squama fulcrantes, when they have in their axils tufts or fascicles 

 of leaves. Occasionally these leaf-scales, by an excess of deve- 

 lopment, develop into true linear leaves arranged spirally, and 

 each separated from its fellow by an internode of considerable 

 length. Leaves of this character occur frequently on the lower 

 part of the shoots of the year, as in Pinus Sabiniana, Pinea, sil- 

 vestris (sometimes), and other species. In some cases even they 

 are produced from old woody branches or even from the trunk, 

 as in Pinus cdulis, Parryana, rigida, Jchasyana. 



* See Linnaeus, Syst. ed. Ginelin, 1791, p. 1072 ; Tristan in Ann. du Museum 

 (Mem. sur le genre Pinus, p. 242); Engelmann, Trans. Acad. St. Louis (J880). 

 vol. iv. tab. i., Pinus Elliotti. 





















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