Metaphyta L ilium. 



153 



space in the fundamental tissue of the leaf. This funda- 

 mental tissue is composed of chlorophyll -bearing cells, 

 which are, next the epidermis, arranged in one or more 

 regular layers and termed palisade parenchyma, whilst to- 

 wards the middle of 



FlG> 7I '~ A ' EPIDERMIS OF Leucojum Ternum. 

 B. TRANSVERSE SECTION OF EPIDERMIS OF 



tV>A 



form What is known ********* umbellatus. (Behrens.) 



as the mesophyll, 



or spongy paren- 



chyma. Through 



the mesophyll run 



the fibro-vascular 



strands, which are 



similar in structure 



to those of the stem. 



The xylem lies next 



the upper surface of 



the leaf, since that 



is morphologically 



the side next the 



centre of stem. 



From either epider- 



mis (though not in 



that of the type we 



are considering) 



arise epidermal 



hairs, which are 



prolongations of ep- 



idermal cells (fig. 



72). Such hairs are 



termed unicellular 



when their cavities 



are continuous with 



those of the cells of which they are prolongations. Fre- 



quently, however, these hairs become multicellular by the 



subdivision of their cavities into chambers. A number of 



s, guard-cells containing chlorophyll grai 

 1 cells ; k, nuclei ; h, 



cuticle ; e, epidermal 

 /, general parenchyma. 



ins, a ; c, 

 air-space ; 



