LEAF 207 



4. The conventional way of describing leaves is to begin 

 with their arrangement on the stem, then to continue with the 

 description ,of the leaf-stalk and the stipules, then to state 

 whether it is simple or compound and to proceed to its general 

 shape, its base and apex (if distinctive), its margin, surface, 

 texture, venation and colour. 



5. Metamorphosed Leaves. — The leaves of one and the 

 same plant are by no means always all of the same shape. As 

 they answer different purposes, they are modified in shape. The 

 main function of the foliage leaves is, as we shall see hereafter, 

 the absorption of gaseous food from the air. Now, the seed- 

 leaves, to begin with the first leafy structure of a plant, have to 

 supply food to the young plant! et, and such food may be stored 

 in the seed-leaves themselves (Horse Gram, p. 30) or in a separate 

 tissue of the seed, the endosperm, which the seed-leaves have to 

 absorb (Castor, p. 123, Maize, p. 169, Cocoanut, p. 139). Their 

 shape, is therefore, such as to suit these special functions and 

 often widely differs from the shape of the foliage leaf of the 

 same plant. 



Then, there are the leaves of the lower parts of the stem 

 which are often rudimentary. Thus, for instance, in the Bamboo 

 they consist only of the sheaths of the foliage leaves. In the 

 underground stems of the Onion, the Potato, the Canna and 

 similar plants they are scaly. We find such scaly leaves in the 

 resting buds of woody stems as well, and here they represent the 

 leaves at the bases of fresh shoots. 



Again, the bracts, leaves found on the flower stalk, must be 

 considered modified leaves. They differ from foliage leaves in 

 size, shape and sometimes in colour also (see Adhatoda, p. 101, 

 Sunflower, p. 64, Bougainvillea, p. 128). 



The modification of leaves finds another expression in those 

 plants, in which two kinds of foliage leaves occur on the same 

 stem, as for instance in Emilia sonchifolia, where the lower 

 foliage leaves forming a leaf-rosette are stalked and round, 

 whereas those higher up on the stem are sessile and lyrate with 

 auricled bases. 



Specialized forms of leaves are 



