CH. Jl] SIMPLE AND COMPOUND LEAVES 15 



between the fingers, when the venation is found for the 

 most part to resist the strain much better than the softer 

 tissues in which it runs. 



If, still confining our examination to the ordinary green 

 foliage-leaves, we compare a large number of different 

 kinds, selected from common plants, a broad distinction 

 between two great categories of leaves rapidly forces itself 

 upon our attention. While many of them agree with 

 those mentioned in having a simple and undivided, or 

 unbranched, lamina, others are found to have the lamina 

 more or less cut up into segments, or to be branched in 

 various ways. 



Everyone would at once distinguish sharply between 

 the simple leaves of the Bay Laurel, Beech, Nettle, Bam- 

 boo, Water Lily and Rhododendron, for instance, on the 

 one hand, and the compound leaves of the Horse-chestnut, 

 Laburnum, Robinia, Ash, Sensitive Plant, and Maidenhair 

 Fern on the other ; insisting on the fact that whereas the 

 former present in each case a definite whole, with one 

 blade and one stalk only, the latter are more or less 

 obviously branched so that several blades are fixed on 

 to a common stalk, from which they can be detached 

 one by one. 



If we extend our comparison to leaves such as those 

 of the Oaks, White Poplar, Pyrus torminalis, Fig, Haw- 

 thorn, and some others, however, it becomes evident that 

 a series of examples can be selected which commence 

 with perfectly simple leaves and pass into compound ones 

 by insensible gradations. Hence it is necessary in practice 

 to take some mark by which we can distinguish the two 

 kinds. 



It is clear that the mere degree of incision of the leaf- 

 blade does not decide the matter, for botanists term the 

 leaf of the Celandine or the Hellebore simple, while that 



