132 Professor Alexander Dickson on the 



number of longitudinal veins run nearly parallel to one 

 another from base to apex, towards both of which they 

 converge. One of these veins occupies the middle line, is 

 considerably stronger than the others, and constitutes a 

 distinct midrib projecting somewhat on the lower leaf- 

 surface. It is to be noted that, as we pass from the midrib 

 outwards, every fourth vein is considerably stronger than 

 the three intervening ones. Of the stronger longitudinal 

 veins, there are from 5 to 9 on each side of the middle 

 line. Between the longitudinal veins, small transverse 

 veinlets extend, forming a somewhat rectangular net-work. 

 The upper surface of the blade is of darker colour than the 

 lower. The upper epidermis is almost wholly destitute of 

 stomata, while the low^er is well supplied with them. 

 The stomatic guard-cells contain numerous well-coloured 

 chlorophyll-bodies, and are for the most part so placed 

 that the slit is parallel to the long axis of the leaf. The 

 chlorophyll-parenchyma towards the upper leaf-surface con- 

 sists of about four layers of somewhat closely packed cells, 

 which, instead of exhibiting the ordinary pallisade-form, 

 are slightly flattened parallel to the surface. That towards 

 the lower surface is somewhat thinner, consisting of about 

 three layers of cells, rather more loosely arranged. Between 

 the upper and lower chlorophyll-parenchyma, there are 

 (just as in the cladodes of this and other species of Ruscus) 

 about two layers of somewhat irregularly shaped cells 

 destitute of chlorophyll, and with rather firm walls. The 

 fibro-vascular bundles exhibit a well-marked scleren- 

 chymatous sheath, and the position of the phloem and 

 xylem elements is normal ; i.e., the xylem is towards the 

 upper, and the phloem towards the lower leaf- surface. 

 The petiole is about 5 inches long, and is somewhat flattened 

 where it passes rather gradually into the lamina. About 

 its middle, it is nearly semi-cylindrical (Plate IX. fig. 

 3) ; convex externally or below, and nearly plane internally 

 or above. Lower down, the inner face becomes concave ; 

 and it is more and more channeled as it is traced towards 

 the base, wdiich is expanded and sheathing, with somewhat 

 scarious margins. Between these foliage-leaves and the — 

 in this plant — much more familiar leaf-scales, transition 

 forms are to be seen, where the sheathing base is more 



