THK LEAK. • 



them in evory <lircctioii. j,'iviiig eiirli its slmn* of room mid cx- 

 jxHiiro t(< lijjht and air, and to boar tlio flowers and si-t'ds. 



" Till! Hteni, in fact, is tlm af^cncy by which the work of indi- 

 vidual U'avcs is coinbint'd and concentrated for the j^cncral benefit 

 of the plant. Kach separate leaf, like each sej)arate cell, has a 

 life of its own, and to sonu* extent is independent of every other 

 leaf : but if they are to be of any nse to the plant as a whole, there 

 must be coo[)eration.*' (Masters' Plant Life.) 



The (explanation for the ascent and movement of tlii' "sap" in 

 jilants is by no means simple and easy. The swaying' of the 

 stems, branches, and leaves by tiie wind renders some assistance. 

 The chemioal changes j^oing^ on within the jjlant cause some 

 movenu'nts of the li(|nid nniterials. The evajjoration from tlie 

 leaves helps "draw" the water and gases from l.low to ascend 

 and fill the spaces which would otherwise bo vacant. "There is 

 no continuous tube or set of tubes, and there is no fluid of uni- 

 formly the same composition throughout. Xoar the root the 

 juice of the plant has one composition, near the leaf another. 

 The word 'sap,' then, though convenient, must not be used or 

 conceived of as indicating the existence of a curr'^nt absolutely 

 fixed in its direction or uniform in its composition." (Masters* 

 riant Life.) 



The Leaf. Springing from the sui)orficial part of each node, 

 and generally completely surrounding the culm, appears a leaf, 

 the sheath or lower part of which is generally nnivithite or wrapjied 

 around the culm. The leaves are ffni-rdiiiril or ilistichons, and 

 are so placed that each leaf is a little above or below any s))cciiil 

 one selected and exactly half way around the stem, where tlic 

 blade spreads away from the stem. Usually there is one leaf 

 at a node, but in Cynndon Ddrfi/Inii (Bermuda grass). Spurohohis 

 urenarixs, and a few others, there are apparently two or three at 

 a node distichously i)laced above each other. 



The Sheaths of the leaves are usually spoken of as split on 



