LEAVES AND ROOTS— THEIR FUNCTIONS AND STRUCTURE. 



319 



be contained in the ascending sap ; and if 

 so, it is also evident that it must he carried 

 into the ascending sap vessels by means of 

 the centre vessel, which I have already 

 described, as running the whole course of 

 the rootlet, and traversing the thickness of 

 the bark of the root, until it joins the be- 

 fore mentioned ascending vessels. The 

 external coat of the rootlet is, as I have 

 already stated, given off from the external 

 coat of the root, and, consequently, the 

 proper juice of the plant in the root, and 

 given into the rootlet, is, in the latter, ex- 

 posed to the action of the atmospheric air 

 and the water contained in the soil ; and 

 thus, having been modified and diluted, it 

 enters the centre vessel in a fit state for the 

 due nourishment of the plant. 



In confirmation of these views, I may 

 call to your recollection the phenomenon 

 exhibited by a grafted tree. Here we see 

 on the same stock a variety of fruit. Now, 

 on what does this depend ? The answer 

 will be, on the scion, or bud, introduced. 

 True, it is so ; in that scion or bud is con- 

 tained the germ of young leaves ; these, 

 by the nourishment supplied, are evolved, 

 and then commences, according to the cha- 

 racter of the leaf, the elaboration of the 

 proper juice which is to produce that par- 

 ticula?- variety of fruit. The fact, also ob- 

 served by florists, and mentioned by a cele- 

 brated culturist in Philadelphia, of the loss 

 sustained by cutting off the young branches, 

 containing the buds and flowers of camel- 

 lias, causing the rootlets to die,' — showing 

 that certain rootlets depend upon certain 

 branches or leaves, which, having been 

 cut off, the rootlet dies, as being of no fur- 

 ther use. This is an important and inte- 

 resting truth. Again, let us look to the 

 fact of the maple affording its sugar from 

 the concentrated juice of the former year, 

 and giving it out whenever the sap begins 



to ascend, and before any leaf has yet ap- 

 peared. At the same time, it is known that 

 if the tree is bled too much, it destroys the 

 luxuriance of the vegetation for that sea- 

 son. Again, let us watch the progress of 

 the young fruit tree. Deriving the nourish- 

 ment required, in the first place, from the 

 immense accumulation of vegetable mat- 

 ter in the cotyledons, the root of the young 

 plant thrusts itself into the earth, and the 

 young leaves unfold themselves to the at- 

 mosphere. Year after year crops of leaves 

 succeed each other, — each leaf performing 

 the important function assigned to it, of 

 assimilating a portion of the sap in the 

 progress of its circulation into the proper 

 juice of the plant, which, when done, it 

 dies and falls to its mother earth. Season 

 after season our plant gains strength ; its 

 leaves are thrown out stronger and larger, 

 and, in due time, the tree is capable of 

 yielding fruit. With the first appearance 

 of the leaves of the following season, the 

 plant is decked with flowers, succeeded by 

 fruit. This is the progress of a tree, from 

 its first germination to maturity. Here we 

 see the great importance of the leaves, in 

 maintaining the plant. If our plant is 

 puny, its branches slender, and its leaves 

 wanting in luxuriance, we cannot look for 

 fruit ; and in this case, what is our reme- 

 dy ? We apply the pruning knife ; and 

 thus, by concentrating the ascending sap, 

 instead of being distributed over a large 

 surface through many long branches, we 

 give energy to the plant, and leaves and 

 flowers burst forth in great luxuriance.* 



* It is on this principle that Dr. Klotschs at- 

 tempts the cure of the potato ilisease, — '<to pinch 

 off about half an inch from the top of the plant, 

 when it has reached a height of six or nine inches, 

 and to repeat the same operation 10-11 weeks af- 

 ter the time of planting, on all the stems of the 

 plant." By this operation, the carbon of the plant 

 is not again expended in the production of new 

 stems and fruit, but is thrown into the tubers, pro- 

 ducing potatoes of firmer texture, and more con- 

 centrated material. 



