FOLIAGE. 139 



by placing the model at different angles to the light of 

 a candle a whole series of shadows corresponding to 

 actual leaf shapes may be seen. 



It must also be remembered, that a very large pro- 

 portion of wild plants never have any chance of catching 

 all the light that falls on them. They grow amongst 

 many other species, and have to develop their leaves in 

 any opening which thfy can find. In a grass field, for 

 example, most of the leaves are long and narrow, or 

 " linear," and most of the weeds which grow there, 

 either have leaves like the grass, such as Plmitago lan- 

 ceolata, Mouse-ear Chickweed, Knot-grass, etc., or their 

 leaves, like those of the Butter-cups, are finely divided, 

 and cut up into thin segments, which can sway freely in 

 the wind, and adapt themselves to their special circum- 

 stances. 



It is, however, abundantly clear, that the shapes of 

 the leaves which make up either the foliage dome of a 

 Horse-chestnut or the interlacing criss-cross of blades in 

 a pasture field, are such that in Britain, at any rate, the 

 tint of the landscape is always green, and entirely masks 

 the colour of the soil. 



The arrangement of the cells which make up the leaf 

 is entirely controlled by the necessities of their work. 

 This can be easily seen by examining, for example, 

 a transverse section of the leaf of Skimmia or Laurustinus. 



As will be seen from the • diagram of such a 

 section, there are from above downwards : ( i ) The 

 single layer which forms the upper skin or epidermis 

 with thickened outer wall. (2) One or two layers of 

 somewhat drawn-out or lengthened cells, the "palisades" 

 full of the rounded chlorophyll or leaf-green bodies. If 

 is in these cells that the sugar is formed. (3) The 

 irregular mass (to the right) in a cavity lined by small 



