THE ANGIOSPERMAE : LEAVES 



953 



The peculiar form of leaf called peltate deserves a special mention. This 

 is a mushroom-shaped structure with the petiole apparently attached at or 

 near the middle of the underside of the lamina. In many cases {e.g. Hydro- 

 cotyle vulgaris and Cotyledon umbilicus) the seedling plants show a series of 

 stages illustrating that the mature peltate leaf has developed from a cordate 



B 



D E F 



Fig. 939. — Tvpes of Palmate division in simple leaves. A, Palmate ; Acer. B, Palmatifid ; 

 Delphinium. C, Palmatisect ; Geranium. D, Palmatilobed ; Fatsio. E, Emargmate ; 

 Liriodendron. F, Pedate ; Hellehorus. 



form, the basal lobes of which have coalesced so as to produce an orbicular 

 outline. 



The size of the leaves on any individual plant is characteristic of the 

 species and does not vary very widely, for leaves are organs with limited 

 growth and the size ultimately reached depends chiefly on hereditary factors. 

 Some differences of size exist between young and old plants and between 

 those growing in the shade and in the sun. Young plants and young shoots, 

 such as the stool-shoots which spring from the base of a bush or tree that 

 has been cut down, may produce leaves of unusually large size, owing to their 

 31 .\ 



