Hknkv and Flood — The Dimkcld Ilijbrid Larch. 63 



presence of papillae on the cells of the epidermis ; in the position and size of 

 the fibro-vascular bundle. These characters are not always identical in the 

 two kinds of leaves (those of the long shoots and those of the spurs). 



These distinctive microscopic characters are set out in the following 

 statement : — 



(1) Eesin-canalsof the pulvini of the young twigs, circular in L.ev/i'opaea, 

 oval in L. hptolejiis, oval in L. cnrohpis. 



{2) Eesin-canals of the leaves of the long shoots : — L. curopaea — well 

 developed, situated at the extreme outer edge of the leaf, equidistant from 

 the upper and lower surfaces, separated from the epidermis by one layer of 

 lignified cells. 



L. leptolepis — well developed, situated nearer the lower than the upper 

 surface, not quite at the extreme outer edge, separated from the epidermis 

 above by two or three layers of cells, abutting on the epidermis beneath. 



Z. eurolepis — well developed, situated as in L. curopaea, but separated 

 from the epidermis by either one or two layers of cells. 



(3) Resin-canals of the leaves on the short shoots : — 

 L. europaea — minute and indistinct, or obliterated. 



L. leptolcpis — small but distinct, with a lining of large cells, and 

 separated from the epidermis by lignified cells. 

 L. eurolepis — minute and indistinct, or obliterated. 



(4) Epidermal cells of both kinds of leaves : — 

 L. curopaea — aW smooth. 



L. leptolepis — all papillate. 



L. eurolepis — cells on the central part of each surface and on the outer 

 edges, with papillae ; elsewhere the epidermal cells are smooth. 



(5) Fibro-vascular bundle of both kinds of leaves : 

 Z. europaea ; small, equidistant from both surfaces. 



Z. leptolepis; large, nearer the lower than the upper surface. 

 Z. eurolepis ; large, equidistant from both surfaces. 



(6) Stomatic lines of the leaves. These occur as two bands, one band 

 on each side of the midrib, and are usually present on both surfaces. The 

 position of the stomata are marked out by white wax; but the lines are 

 rather irregular in number and arrangement, being seldom continuous from 

 base to apex. In the subjoined table, the number of lines in each band is 



indicated : — 



Long shoot leaves. Short shoot leaves. 



Upper surface. Lower surface. Upper surface. Lower surface. 

 Z. eurojjoca, 2 or 3 3 or 4 1 or 2 or 3 



Z. leptolcpis, 3 or 4 5 or 6 2 or 3 3 to 5 



Z. eurolepis, 2 or 3 4 or 5 1 3 to 4 



R.I.A. PKOC, VOL. XXSV, SECT. B. [K\ 



