HO WILL TUB EES GBOW A FT EE THE DESTRUCTION OF LEAVES? 



surface, and the earth drawn over the plants an inch thick. 

 This was done to two rows, leaving double the quantity of the 

 same crop in its natural state. Yesterday the Potatoes of both 

 were drawn : in the rows left untouched, two-thirds of the crop 

 were found to be more or less affected ; but in the rows on 

 which the experiment was tried, every Potato was found perfect, 

 and in size and quantity the same as the others. I beg to add 

 that the same result followed a similar experiment, made in a 

 garden bv one of mv workmen, upon a small crop of 1 Snow- 

 balls.' " 



Here then is a result diametrically opposite to that obtained 

 by others, and in accordance with the statement of M. Tombelle 

 Lomba. The experiment must, therefore, be repeated. It is 

 probable that the discrepancy in the results arises from the 

 plants under experiment not being in the same stase of growth. 

 It appears to me essential to success that the flowering shall 

 have been completed, and that the fruit shall have begun to 

 form. At that time the office of supplying the tubers with 

 matter from which they may organize their starch is nearly over, 

 and the leaves are chiefly occupied in the nutrition of the 

 growing fruit ; so that the loss sustained by the tubers may be 

 little or nothing. 



That tubers and roots will grow for many years, although their 

 tops are removed, is an undoubted fact, be the explanation of the 

 process what it may. It is now seventeen years since M. Du- 

 trochet brought to the notice of physiologists the unexpected fact 

 that in the Jura may be found the roots of fir trees still alive 

 and growing, at the end of forty-five years after the trunks were 

 felled. A similar example is recorded by the Rev. Mr. Berkeley 

 in the case of an Ash Tree which had been sawn over level with 

 the ground. (See 'Gardener's Chronicle/ 1850, p. 99.) Gar- 

 deners know very well that the tuberous Tropseoliuns. the stems 

 of which have been accidentally broken off, will continue to grow 

 for a long time afterwards : as also will tuberous Bindweeds. 

 These are notorious facts, though they have never been recorded 

 with the exactness which is desirable in scientific questions. And 

 it so happens that I have now before me a very illustrative 

 case, which places the matter beyond all further question. 



It chanced that in the Conservatory of Chiswick House a plant 

 of Sello's Ipoincea was, in November, 1840, destroyed to the 

 ground by frost, since which period it has neither made buds nor 

 leaves. Nevertheless, its roots have continued increasing rapidly 

 in size. In fact, it has been frequently repotted as its increase 

 in size demanded it; for in 1840, at the time of the accident, it 

 was but a small root. During this long period it has been sub- 

 jected to a high temperature At this moment the root forms a 



