98 NATURAL SCIENCE. Aug., 



examination of the leaf-forms of one or two very widely distributed 

 genera. Quoting from Pax's monograph on the genus Acer, he presents 

 to us first the species belonging to Europe : Acer platanoides, which in a 

 wild state inhabits damp localities, and the Sycamore (A . pseitdo- 

 platanus) have pointed leaves ; the Maple (A . campestre) grows 

 on the plains and uplands of Central and Southern Europe, 

 and the lobes of its leaves are blunt, as are those of A. mon- 

 spessulanum, also from Southern Europe. In the United States 

 and in Japan, the different species have leaves with long pointed 

 lobes, and this feature is still more marked in the Himalayan 

 varieties. Acer integrifolia, from Southern China and Japan, has a simple, 

 entire leaf which ends in a long point. Though he does not (without 

 other evidence) refer plants without Triinfelspitzen to a dry climate, 

 yet he concludes that when they possess this feature so strongly 

 marked as in Ficus religiosa and others, they must grow in a country 

 with a heavy rainfall. Stahl thinks also that this peculiarity, which 

 is so entirely one of adaptation to climate, might throw some light on 

 the conditions of growth of fossil plants. 



In plants wholly confined to the tropics, many young leaves 

 assume a hanging position on unfolding, and remain vertical for some 

 days after attaining their full size. This is undoubtedly a protection 

 from the heavy rain, and saves them from the devastation that over- 

 takes so much of the vegetation in these destructive showers. When 

 the leaves are stronger they become horizontal, though some very 

 large leaves, as those of Anthurium Veitchii, remain vertical throughout 

 their life. It would be interesting and useful to be able to calculate 

 the exact force of the rain-drop as it strikes the leaf. This has 

 not been worked out, but that the blow is heavy anyone knows who 

 has been caught in one of these showers, or who has heard the 

 noise made by the rain falling on palm leaves. Kny, in the Berichte 

 dev deutschen botanischen Gesellschaft, 1885, has directed attention to the 

 danger incurred by leaves from rain and hail, and to the leaf-tissues 

 and leaf-forms specially adapted to meet this emergency. In simple 

 undivided leaves we find either great elasticity and bending power ? 

 or a strong leathery structure. In other leaves we have division into 

 laminae ; either, as in many palm leaves, this takes place regularly by 

 the splitting of a layer of cells as the leaf unfolds, or it is effected later 

 by a tearing apart of the tissue. The division reaches its highest 

 development when the laminae are quite separate leaflets, as in most 

 ferns and in many dicotyledonous plants. 



The adaptation of leaf-form to function and environment is 

 nowhere more strikingly seen than in those plants that at different 

 times produce different kinds of leaves. The first leaf of the stately 

 fern Platycerium alcicome is unstalked and kidney-shaped, the mantle- 

 leaf of Goebel, 2 and lies flat on the ground, thus protecting the young 



2 " Morphologische Studien. — I. Ueber epiphytische Fame u. Muscineen." 

 Annates du Jardin Bot unique dc Buitcnzorg, 1887. 



