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ANATOMY, ASTD LIFE-HISTOBY OP THE CONIFEBJS. 263 



of Lycopodium and Isoetes is obvious. In fossil plants referred 

 to Libocedrus, Glyptostrobus, Callitris, Cyparissidium, and other 

 genera from geological formations of different epochs, the same 

 pleiomorphism in the foliage may be observed as in existing 

 genera. It is therefore probable that these diversities in foliage 

 are not so much the result of direct inheritance from an ancestral 

 condition, or of a sudden reversion to it, as of some circumstances 

 which at one time arrest, at another stimulate development and 

 growth. If this be so, the primordial or protomorphic leaves are 

 the outcome of a similarity in the environment, common alike to 

 archaic and to existing time. This is borne out by the fact that 

 where growth and development are both very rapid, as in those 

 precocious buds which develop into shoots during their first 

 season of growth, or those which result from injury, such as the 

 removal of the terminal bud by the pruning-knife or otherwise, 

 there the bud-scales exist in the form of primordial leaves. 



Leaves on the Fertile Branches. 



Apart from the occasional transitions to be met with between 

 the ordinary foliage-leaves and those of the male or female 

 flowers respectively, perfectly formed leaves may be found on 

 the cone-bearing shoots of a different form to those on the barren 

 shoots. This happens in some silver firs, as Abies amabilis and 

 A. subalpina. In A firma the leaves on the fertile branches are 

 different both in form and internal construction from those on 

 the sterile one ; thus, in the form of the Japanese A. firma known 

 as bifida the leaves are longer and deeply notched and the resin- 

 canals are subepidermal, whilst in the typical firma the leaves 

 are shorter, blunter, and the resin-canals are in the centre of the 

 niesophyll. As each form of leaf occurs (for a time at least) on 

 particular trees to the exclusion of the other, it is no wonder 

 that they were considered to characterize two different species, 



firma and A. bifid 

 the latter. On the < 



Maries, art A rst\* 0™, l,o 



Mr. John Veitch, M 



discovery. 



Japan, of the two kinds of leaves growing on the same branch. 

 Indeed, on the leader-shoots of trees growing in this country, 

 leaves of the two forms may be seen on the same shoot, bifid 

 ones below, entire ones above *. 



Ma 





to the literature of the subject are given 













