HYACINTH LEAF 175 



a. Two narrow guard-cells, which inclose the pore. 



b. Two triangular subsidiary cells, which com- 

 pletely surround the convex side of the guard-cells. 



Compare this view of the stoma with the same 

 structure as seen in transverse sections of the 

 lamina. 



V. Cut tangential sections of the upper surface of 

 the lamina. (1) Mount some, and examine them under 

 a low power. (2) Treat others with nitric acid; dry 

 them, and ignite on platinum foil over a spirit-lamp. 

 Mount the ash in water, and examine under a low 

 power. The structure will resemble that of (1). 



Treat with acetic acid : no evolution of gas. 

 Treat with nitric acid : it is not dissolved. 

 The residue is a silica-skeleton of the epidermal 

 tissues. (Compare p. 90.) 



VI. Transverse sections should also be cut from the 

 foliage-leaves of the Hyacinth, which, as above noted, 

 grow in an almost vertical position : mount in glycerine, 

 and note under a low power that there is no great 

 difference between the upper and lower surfaces as 

 regards the disposition of the tissues, excepting that 

 the orientation of the collateral bundles is such that 

 the xylem is directed towards the upper surface. 



Stomata may be seen both on the lower and upper 

 surfaces : there is no distinctly marked palisade-paren- 

 chyma : centrally is a mass of colourless thin-walled 

 parenchyma. Note the absence of strengthening 

 sclerenchyma. 



This will be found an excellent opportunity for the 

 study of the details of a simple stoma : observe that 

 the guard-cells are about at the general level of the 



