PROCEEDINGS OF THE FARMERS' CLUB. 293 



gone to form an immense mass of leaves, is disposed of for the 

 rapid growth of the head. 



Potato tops, in my opinion, should never be cut off, as is prac- 

 ticed everywhere 5 when this is done partially a great number of 

 small potatoes are immediately developed, and when entirely 

 there is no more growth of tuber. 



Potatoes are not formed until the vine has made a complete 

 growth ; the buttons then appear, and may be pinched off with 

 great advantage to the tuber, as at that period the sap requires 

 to be stopped that the tuber may be formed. Shortly after this 

 period, bend the top, and fasten it down with a small parcel of 

 earth, which will produce a great development under ground, 

 and amply reward the agriculturist for the trouble. If corn is 

 topped at the proper time, it will add largely to the yield. 

 Tobacco may be pinched at a certain stage of its growth, and 

 leaves will form 2| feet long, and 14 inches wide. 



It is not the loss of watery vapor alone that produces these 

 effects when plants are topped ; because, beside these, all plants 

 exhale at the same time volatile compound in less or greater 

 quantities. We are familiar with the fact that such exhalations 

 arise from the petals of all flowers, often of an odoriferous char- 

 acter ; by the emission of these matters the trimmed plant no 

 doubt relieves itself of what would prove injurious if retained. 

 Of the chemical nature of these exhalations little or nothing is 

 known. 



If a branch of a living tree is bent so that a few of its leaves 

 can be placed under the edge of an inverted tumbler of water, 

 and then exposed to the influence of the sun's rays, bubbles of gas 

 will immediately form on each leaf, and after a short period of 

 time will rise through the water and collect on the bottom of the 

 tumbler. 



When vapor escapes from the leaves more rapidly than the 

 supply of water from the roots, the leaves wither. You often 

 observe this in growing crops in hot weather. 



The ascent of the sap is generally modified by the season, heat 

 of the weather, and age of the plant. During winter the circula- 

 tion is very slow, and increases as the season a-dvances. The 

 sun's rays accelerate the movement of sap much more than the 

 temperature of the atmosphere, which is shown by the fact that 

 in winter there will be a circulation on the side where the sun 

 falls, when it will be stagnant on the opposite side. This will 



