MAIZE LEAF 173 



II. Cut transverse sections of the lamina ; mount in 

 water, or dilute glycerine. 



Other sections may be treated with alcohol to expel the air- 

 bubbles ; the chlorophyll will, at the same time, be dissolved out : 

 the sections may be mounted in chlor-zinc-iodine, and kept for 

 comparison with the above. 



Examine with a low power. 



The section presents a sinuous outline, correspond- 

 ing to a certain extent to the arrangement of the 

 main vascular bundles : at the midrib the section 

 widens out. Note the following arrangement of 

 tissues : 



1. Covering both surfaces of the leaf is an epidermis, 

 resembling that of the stem, but bearing hairs of 

 various form, mostly simple, conical : the largest of 

 them are surrounded at the base by an outgrowth of 

 the neighbouring epidermal cells. 



Note the stomata on both surfaces, with small guard- 

 cells, surrounded by two subsidiary cells : these will be 

 further examined below. 



2. Vascular bundles of various size, which, in the 

 thinner part of the lamina, lie in a median position 

 between the two epidermal layers. The largest of 

 these correspond in structure to those of the internode, 

 the smaller ones are reduced forms of the same type. 

 Note that the spiral and annular vessels (i.e. protoxyleni) 

 are nearer the upper surface of the leaf. 



Between the epidermis on either side, and the larger 

 bundles, are masses of sclerenchyma, which, together 

 with the bundles, form complete bridges of rigid tissue 



