PLANT PHYSIOLOGY AS REF.ATED TO PRUNING 



23 



or storage is occurring. It remains only to be mentioned 

 that each rootlet and each leaf are more or less directh' 

 connected by \-ascuIar bundles in more or less definite 

 number, depending upon the species. In leaves these 

 bundles constitute the "ribs" or veins which serve both 

 as conduits and as stiffcners of the leaves themselves. 



28. Chlorophyll, the green coloring matter of plants, 

 is the most intimate link which bindslifetothesun. Itisthe 

 laboratory in which is made the earth's supply of organic 

 matter, including all fuel. Though sometimes obscured 



C/i/oron^asi- 



Fa/is ade oarcnc/iyma 



Phloem 



If, -dermis sToma ^orderj^arench^ma 



FIG. 17— DIAGRAM OF CUT EDGE OF LEAF 

 Note the various tissues. (After Stevens, Plant Anatomy.) 



by other colors, it is characteristic of all higher plants, 

 alga:- and mosses, but is absent in fungi. Plants contain- 

 ing it may grow in partial shade or in the full glare of the 

 sun, but never in total darkness. The relation of light to 

 chlorophyll is clearly indicated by the sizes and forms 

 of the leaf blades, the arrangement of leaves upon their 



