. Journal of genetics. larger longitudinally running veins aie raised somewhatabove the general surface of the leaf, the smaller veins are quiteinvisible. In (Plate V, fig. 8), however, all but the very smallest veinsstand up prominently above the surface in the form of a networkcovering the entire under surface of the leaf. There is a correspondiug difference in the upper surfaces of theseleaves; being quite smooth except for slight depressions along themidrib and some of the larger veins, while the whole upper surface is covered with a conspicuous network of furrows. As will
. Journal of genetics. larger longitudinally running veins aie raised somewhatabove the general surface of the leaf, the smaller veins are quiteinvisible. In (Plate V, fig. 8), however, all but the very smallest veinsstand up prominently above the surface in the form of a networkcovering the entire under surface of the leaf. There is a correspondiug difference in the upper surfaces of theseleaves; being quite smooth except for slight depressions along themidrib and some of the larger veins, while the whole upper surface is covered with a conspicuous network of furrows. As will be seen from figs. 10 and 11 of Plate V, the hybrids areintermediate between these two conditions, the reciprocals differing in 80 Species Hyhrids of Digitalis that each follows the maternal type. The upper surfaces of the leavesshow similar peculiarities. That the above differences are due not merely to degree of pro-minence of the veins but also to a dissimilar system of venation maybe seen from text-figs. 22— 25DGxDP Figs. 22—25. These are camera lucida drawings of leaves bleached in Mayerssolution, stained in safrauin and afterwards cleared and mounted inCanada balsam. In there is a network system of large veins,whilst very fine veins fill up the meshes of this network. In , onthe other hand, the only large veins are the midrib and a few longi-tudinally running laterals (which are much smaller than the large veinsof )—the rest of the system consisting entirely of veins all of much W. Nbilson Jones 81 the same size and considerably broader than the finest veins of reciprocals (text-figs. 24 and 25) differ from one another in thegreater resemblance to the seed-parent in each case. 14. The margins of the leaves also show well-marked of is c<iarsely crenate and (presumably by its more rapidgrowth relatively to the rest of the leaf) crinkled so that it cannot bemade to lie flat (text-fig. 34). The margin of is serrate,
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