THE LEAF 85 



the leaves in a large dish of water. Gently brush the 

 leaves with a stiff camel's hair brush, and if the leaves 

 have been boiled enough the soft parts can be removed 

 and the veins left forming a skeleton leaf. 



With care it will be found possible, on other leaves 

 boiled in the same way, to strip off a thin colourless skin 

 from the upper and lower sides, leaving a middle portion 

 consisting of the veins and the soft tissue. Examine 

 the upper and lower skins with a hand lens, and see if 

 any of the minute pores or stomata can be made out. 



Compare all the leaves which can be obtained, and 

 note the arrangement of their veins, whether netted or 

 parallel. Examine the stems of the same plants and 

 see whether, as a general rule, you find stems with 

 dicotyledonous structure bearing leaves with netted 

 veins, and monocotyledonous stems parallel-veined 

 leaves. 



Take leaves of the iris, and pull off a portion of the 

 outside layer of the leaf (this layer is very thin and care 

 is required, but if the operation is properly done no 

 green tissue will come away). Note that the outer skin 

 is colourless, that the underlying tissue is dark green 

 and soft, and has a number of hard fibrous structures, 

 the veins running through it. The point of a knife can 

 easily be got under one of these, and the vein pulled up 

 like a thread of cotton. 



Transpiration. 



Pick a number of shoots of any ordinary thin-leaved 

 plants, such as dead-nettle, lilac, groundsel. Place some 

 in water and leave others lying on the table. The latter 



