MINUTE STRUCTURE OF LEAVES 



155 



Notice that the green coloring matter is not uniformly 

 distributed, but that it is collected into little particles 

 called chlorophyll bodies (Fig. 120, p). 



166. Woody Tissue in Leaves. — The veins of leaves 

 consist of fibro-vascular bundles containing wood and 

 vessels much like those of the stem 

 of the plant. Indeed, these bundles 

 in the leaf are continuous with those 

 of the stem, and consist merely of 

 portions of the latter, looking 

 as if unraveled, which pass 

 outward and upward from the 

 stem into the leaf under 

 the name of leaf-traces. 

 These traverse the peti- 

 ole often in a somewhat 

 irregular fashion. 



EXPERIMENT XXVm 



of Water from 



Passage __ 



_. , _ , -„i «, spirally thickened cells 



Stem to Leaf. — Place a of the vein- 



Fig. 120. — Termination 

 of a Vein in a Leaf. 

 (Magnified about 345 

 diameters.) 



; p, paren- 

 chyma-cells of the' 

 spongy interior of the 

 leaf, with chlorophyll 

 bodies; n, nucleated 

 cells. 



freshly cut leafy shoot of some 



plant with large thin leaves, 



such as Hydrangea hortensia, 



in eosin solution for a few 



minutes. As soon as the leaves show a decided reddening, pull 



some of them ofE and sketch the red stains on the scars thus made. 



What does this show? 



167. Experimental Study of Functions of Leaves. — The 



most interesting and profita,ble way in which to find out 

 what work leaves do for the plant is by experimenting 

 upon them. Much that relates to the uses of leaves is 



