44 MINUTE MARVELS OF NATURE 



the net-veined leaves of most of our English 

 plants and with flowers arranged in whorls of 

 four or five. Thus, as a zoologist can build up 

 an animal from a single tooth, the botanist can, 

 from a thin slice or section of the stem of a plant, 

 at once gain considerable knowledge of the class 

 of plant from which it was taken. 



And now just a word regarding these string- 

 like bundles of tissue which we find in the stems 

 and leaves. Each bundle, as I have already 

 .shown, originates near the growing-point by the 

 gradual alteration of some cells into long tubes, 

 and on examining these at a later stage, each 

 bundle is seen to consist mainly of two distinct 

 kinds of tissue separated by a layer of delicate 

 cells. The tubular vessels nearest the central 

 pith, when mature, generally lose their proto- 

 plasm or lixKng matter, and usually contain air 

 only, although sometimes liquids are conducted 

 through them. Outside these come the wood fibres 

 which ffive strength to the bundle, and following- 

 these the delicate cells which separates one class 

 of tissue from the other. Those vessels on the 

 outer side nearest the bark are similar to the 

 fibrous wood-cells, but more delicate and filled 

 with mucilaginous matter. 



Now the layer of delicate cells that separates 

 these tissues is a very important tactor to the 



