PINUS. ROOT. 151 



walled, lignified. Note that it is absent below the 

 stomata. 



C. The Mesophyll consists of thin-walled, chloro- 

 phyll-containing parenchyma. The cellulose walls (blue 

 with Schulze's solution) show a peculiar infolding. 

 Resin-passages occur in it. Their cavity is lined 

 with thin- walled epithelium, which is immediately 

 surrounded by a layer of thick-walled sclerenchyma. 



D. The Bundle-sheath, walls stained brown with 

 Schulze's solution. 



E. The tissue within this consists of two elements : 



i. Parenchymatous cells, with thin cellulose walls 

 (blue with Schulze's solution), and protoplasmic con- 

 tents. 



ii. Elements having lignified walls, with bordered 

 pits, and no cell-contents (tracheides, transfusion-tissue. 

 [Mohl.]). 



F. The two central Vascular bundles, the constituents 

 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. 



THE ROOT. 



I. Cut transverse sections of a young primary root of 

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

 treat with dilute potash, and mount in glycerine. 

 Observe : 



1. A thick band of Cortex, not covered externally 

 by any true epidermal layer (cf. longitudinal sections of 

 apex of root). 



2. A Bundle-sheath within the cortex. This is a 



