PINE ROOT 247 



i. Parenchymatous cells, with thin cellulose walls 

 (blue with chlor-zinc-iodine), and protoplasmic 

 contents. 



ii. Elements having liguified walls, with bordered 

 pits, and no cell-contents (tracheides, or trans- 

 fusion-tissue). 



6. The two central vascular bundles, the constitu- 

 ents of which resemble those of the stem. Note that 

 the xylem is directed towards the upper surface. 

 Thick-walled sclerenchyma is scattered irregularly 

 round the bundles. It will thus be seen that the leaf 

 of the Pine is of the centric type. 



Compare the foliage-leaf of the Yew (Taxus), noting its 

 flattened form and short petiole : the upper surface is convex, 

 the lower concave, and there is a clearly marked midrib. 



Cut transverse sections, and observe in them the convex 

 upper surface, covered with an epidermal layer without stomata : 

 there is no hypoderma, and resin-passages are absent from the 

 mesophyll : the latter consists of palisade-parenchyma imme- 

 diately below the upper epidermis, and spongy parenchyma 

 towards the lower. 



The epidermis covering the concave lower surface has peculiar 

 excrescences of the outer wall of the epidermal cells, and numer- 

 ous stomata. Centrally is a single vascular bundle, with the 

 xylem directed upwards. Thus this leaf is distinctly of a 

 bifacial type. 



THE ROOT. 



I. Cut transverse sections of a young primary root of 

 the seedling of Pinus (not necessarily P. sylvestris) : 

 treat with dilute potash, or " eau de javelle," and 

 mount in glycerine. Observe 



1. A thick band of cortex, with a superficial, but ill- 



