XI] DRIP-TIPS, ETC. 121 



accurate fitting in of leaf by leaf or lobe by lobe, like 

 the pieces of a mosaic, has suggested the name of Leaf- 

 mosaic for this phenomenon. 



The manifold shapes and peculiarities of form and 

 surface of leaves are at present inexplicable in detail, 

 though we may suspect that the long pointed apices 

 (drip-tips) of Ash, Norway Maple, Viburnum Opulus, &c., 

 help them to run off superfluous water, which might clog 

 the transpiratory activity if left hanging ; appressed hairs 

 and waxy coverings, glossy surfaces, &c., fulfil similar func- 

 tions in other plants. It has been suggested that the 

 trembling of Aspen and other leaves leads to the same 

 end by shaking off the drops. 



The resinous or gummy and slimy secretions on young 

 leaves bursting from the bud may be rather anti-friction 

 adaptations e.g. Prunus, Alder, Hornbeam, Maples, Ash, 

 Elm, Viburnum, and some Willows, &c. 



