172 PRACTICAL BOTANY 



II. Longitudinal sections should also be cut, when 

 it will be found that the central cylinder consists chiefly 

 of parenchyma, with a few sieve-tubes : note also the 

 central vessel. 



The radial walls of the bundle-sheath may often be 

 well seen, especially in slightly oblique sections : note 

 the wavy outline of the walls, to which the appearance 

 of a dark dot in the transverse section is due. (Compare 

 p. 76.) 



i. LEW BIFACIAL TYPE. 



Note that the phyllotaxis in the Maize is J : the leaf 

 is sessile, and sheathing in its lower half, with a ligule 

 at the upper limit of the sheath ; the form of the 

 lamina is lanceolate, margin entire, ciliate, midrib well 

 marked ; venation parallel ; upper surface hirsute ; 

 lower glabrous. 



I. Treat a piece of the thin peripheral part of a 

 leaf (which has been previously bleached in alcohol) 

 with potash till it is transparent ; mount in glycerine, 

 and examine under a low power. Observe 



1. The parallel course of the vascular bundles. 



2. Their frequent lateral fusion, by means of small 

 branch-bundles. 



3. The absence of stomata above the vascular 

 bundles, and their arrangement in rows in the spaces 

 between them. 



4. The various forms of hair ; and especially the 

 conical unicellular hairs, which give the ciliate character 

 to the margin of the leaf. 



