24 



General Botany 



leaflet and the petiole. The leaf of the orange may be said to 

 be compound because it has such a joint. The fact that some 

 species of oranges have three leaflets gives support to this view. 

 If the leaflets are joined to the end of the petiole, like the fingers 

 of the hands, the leaf is described as palmately compound; if 

 joined to the sides of the petiole, it is termed pinnately com- 

 pound (Fig. lo). 



The leaf made up of tissues. The soft green tissue essential to 

 food production is found chiefly in the blade of the leaf. This 

 may be shown by dissecting a fleshy leaf like that of the common 

 houseleek or live-for-ever. Cutting across the blade of such a 

 leaf, we find that there is a skin covering it above and below. 

 The skin is readily stripped off, leaving the interior of the leaf as 

 a green, granular mass of cells with veins running through it in 

 all directions. The skin is called the epidermis or epidermal 

 tissue (Greek: epi, upon, and derma, skin). The soft tissue 



'!-{ ^Uppcr epidermis 



I \ Palisade layers 



Water- 

 ducting tissue 



Food-con- /Chloroplast 

 ducting ti55ue i ^ 



Bundle sheatky Guard cell 



Lower 

 epidermis 



Stoma 



Fig. II. Model of a small portion ot a leaf from the common periwinkle {Vinca), showing 



cells and tissues. 



