354 



stituting about one-half of the mesophyll, the quota between 

 breadth and length of the cells is ^/2 — ^'з ; the other specimens, 

 including var. Wilanderi had only one palisade-layer which 

 constituted ^/3 — Vi of the mesophyll ; the single palisade-cells 

 were less regular in form than are those of the first-named 

 specimens and their quota was on an average somewhat larger 

 than ^/2. The spongy parenchyma in these leaves was con- 

 siderably looser than that in the former leaves with two pali- 

 sade-layers, and consisted of more abundantly branching cells 

 (Fig. U,C). 



The large bundles are accompanied by some weak stereom. 

 Nestler (1. c, p. 301) records that he found a complete scleren- 

 chymatous sheath ; the specimens which I investigated had bast 

 only upon the upper and under side of the bundles and in 

 greater quantity on the lower surface. Nestler does not mention 

 from whence his specimens originated. 



Fig. 12, В is a somewhat diagrammatic representation of a 

 longitudinal section through the apex of a leaf; the slanting 

 part is the epithema in which the vessels of the bundle spread 

 out and which opens almost at the margin. The cells of the 

 epithema, as was the case in the other species, have strongly 

 undulating walls. 



The leaf-stalk is cordate in transverse section; its cuticle 

 is striped and there is chlorophyll in its epidermis. Five 

 bundles occur of which the median, outwardly-turned one is 

 the largest. The fibrous tissue outside the leptome is fairly 

 strong and on the sides it abuts upon the V-shaped woody 

 parts; the endodermis is slightly lignified on the inwardly- 

 turned part of the bundle, on the outer side it touches the 

 fibrous tissue outside the leptome. There is a large central 

 lacuna. 



R. acer L. 



Lit. Wydler, 1859, p. 267. A. Berlin, 1883, pp. 19 — 21. 

 Hj. Nilsson, 1884, p. 203. Marié, 1885, p. 82. Holm, 1885, p. 



