SCALE-LEAVES, FOLIAGE-LEAVES, FLORAL-LEAVES. 627 



than 90 per cent of the organic matter manufactured throughout the whole 

 . world every year should be reckoned to the account of the green foliage- 

 I leaves. 



I That those members of the plant to which is allotted the manufacture of 



! organic matter should exhibit such a marvellous diversity can hardly astonish 

 I us. For how infinitely varied are the conditions under which this function 

 is performed in the different zones and regions of the globe ! Even within the 

 narrow confines of a restricted area, one may find habitats damp and dry, 

 sunlit and shady, tranquil and tempest -tossed. Nor should we be surprised to 

 find leaves of diverse shape at different heights on one and the same shoot, 

 and that the foliage borne by any plant may exhibit variations in form in 

 successive seasons of the year. And then we must remember that besides the 

 most important function mentioned, foliage-leaves have often to provide for the 

 irrigation of rain-water to the absorbent roots, to play the part of climbing 

 organs, or to serve as weapons ; more than this, they even act as organs for 

 digesting imprisoned animals, with which last function is associated very 

 curious metamorphoses of foliage-leaves. By the segmentation of the leaf into 

 those parts, into the blade, leaf-stalk, and sheath with stipules, an allotment of 

 these various functions becomes possible ; but evidently, in consequence of this 

 division of labour in one and the same leaf, the structure becomes much more 

 complex and manifold. 



A distinctive name has been given to each shape by botanists, who have 

 endeavoured to define the different forms by descriptions. For foliage-leaves 

 alone perhaps a hundred different expressions have been used to shortly desig- 

 nate the most remarkable varieties. Since these terms of botanical nomen- 

 clature can be combined and varied according to the actual facts, we are able 

 to describe the many thousands of differently-shaped foliage-leaves, briefly and 

 tersely, and — what is of especial value, and really the most important aim of 

 these descriptions — another person is able from them to picture the object to 

 himself. 



First of all, let us describe the leaf-blade, the outline of which may exhibit 

 every imaginable geometrical form : obovate, circular, elliptical, rhombic, 

 rhomboidal, triangular, pentagonal, &c. Very often, too, the leaf- blade is much 

 elongated, and the margins are parallel to one another; this is known as linear. 

 The free end of the blade is sometimes pointed, sometimes blunt, and some- 

 times drawn out into a long point ; occasionally, again, it is truncate, pressed 

 in, or cut out in the form of a heart. The base of the leaf-blade may be 

 narrowed and attenuate towards the stem ; or its outline may be kidney- 

 shaped, arrow-shaped, lanceolate, ovate, spathulate, crescent -shaped, &c. The 

 blade is either undivided, when it is termed entire, or the margin is to a 

 greater or less extent indented ; if the indentations are but slight, the leaf- 

 blade is said to be crenate, serrate, or dentate, but if they are considerable, 

 the margin is said to be sinuous or incised ; if, again, the indentations go more 



