THE CONIFERS OF JAPAN. 



511 



surface, into which the midrib is not prolonged (figs. 10, 12). On 

 the horizontal side-shoots the leaves are spreading and more or 

 less twisted at the base, so that the green surface is now upper- 

 most, the glaucous surface beneath, whence arises the apparent 



Fig. 11. 



X-JO- 



Fig. 12. 



::QOOOoOi: 



£boOOO0:- 

 rDooOOCJr 



■ISgggg 



ooxooSs 



OogOoSr 



Apparent under, real upper, 

 surface of the leaf of Picea 

 ajanensis from horizontal 

 branch. 



Diagrammatic section of leaf of P. ajanensis, 

 in its real position. 



position of the resin-cauals on the upper (really lower) surface of 

 the leaf. It may be further noted that on the side-shoots, while 

 the leaves on the underside of the branch spread away more or 

 less horizontally and are twisted, those on the upperside of the 

 branch are placed parallel to the long axis of the branch and 

 are not twisted. Their position therefore is exactly the same as 

 that of the leaves on the leader-shoot. The resin-canals are in 

 contact with the palissade-cells, and are nearest to the green sur- 

 face of the leaves. It is the green surface which is ordinarily 

 most exposed to the light, the glaucous and specially stomati- 

 ferous surface, beneath which there are no palissade-cells, being 

 furthest from the light. Picea sitkensis has the glaucous leaf- 

 surface next the axis, as also many Junipers. 



On the leader-shoot of Abies Nordmanniana the leaves are so 

 twisted that the glaucous surface is away from the axis. It is 

 probable, nay, in some cases, it is certain, that the position of the 

 leaves varies in different stages of growth and according to 

 different circumstances ; but such a movement by torsion cannot 

 affect the internal disposition of the anatomical elements *. 



The resin-canals, when present, are placed on the side of the 

 leaf furthest from the palissade-cells : but in P. ajanensis the 

 resin-canals are in contact with them. Dr. Engelmann has 

 pointed out to me " that in all the Abietineae, probably in all the 

 Coniferse, the vascular bundle consists of an upper layer of wood- 

 * Masters, " Note on Morphology and Physiology of the Leaves of certain 

 Conifers," Journ. Linn. Soc. Bot. voL xvii. p. 547- 



