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 living matter, and usually contain air 

 only, although sometimes liquids are conducted 

 through them. Outside these come the wood fibres 

 which give 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 factor to the 



