THE GRAPE VINE. 



629 



Bugar at a high than at a low temperature." — 

 Theory of HorL, p. 76. 



Day and night temperature in our forcing- 

 houses. — Nature has sufficiently pointed out to 

 U8 that she has for the wisest of purposes estab- 

 lished a difference between the temperature of 

 the day and of the night. She has given man 

 the day to carry on his avocations, and night to 

 take that repose necessary to enable him to 

 renew his vigour for the duties of the succeed- 

 ing day. With similar wisdom, the difference 

 between the temperature of the day and that of 

 the night has been established, that the inferior 

 animals, as well as vegetables, should have their 

 necessary rest also. In constant excitement 

 plants could not exist, therefore they have their 

 diurnal season of action and repose. " In the 

 day, when light is strongest, and its evaporating 

 and decomposing powers most energetic, tem- 

 perature rises and stimulates the vitality of 

 plants, so as to meet the demand thus made upon 

 them; then, as light diminishes, and with it the 

 necessity for excessive stimulus, temperature 

 falls, and reaches its minimum at night, the 

 time when there is the least demand upon the 

 vital forces of vegetation ; so that plants, like 

 animals, have their diurnal season of action and 

 repose. During the day, the system of a plant 

 is exhausted of fluid by the aqueous exhalations 

 that take place under the influence of sunlight ; 

 at night, when little or no perspiration occurs, 

 the waste of the day is made good by the attrac- 

 tion of the roots, and by morning the system is 

 again filled with liquid matter, ready to meet the 

 demand to be made upon it on the ensuing day." 

 —Theory of Bort., p. 90. Such being the order 

 of nature's operations, the forcing-gardener will 

 do well to follow her example ; for he may rest 

 assured that all his other efforts will be in vain 

 if these simple conditions be not complied with. 

 He has it, however, in his power to guard against 

 extremes of temperatures under his glassy cover- 

 ings which he has not in the open air. The 

 natural extreme of heat in these latitudes is sel- 

 dom if ever too great for vegetation, the natu- 

 ral extreme of cold often is. The range, there- 

 fore, of temperature in his artificial climate must 

 not extend to the maximum difference, but 

 nearer to the minimum, because, during winter, 

 when the former takes place, vegetation has sunk 

 into comparative repose; while, during summer, 

 a part of spring and of autumn, when vegetation 

 is in full play, the difference in temperature 

 should be more nearly approximated. The pre- 

 vailing system hitherto followed by many in the 

 regulation of their hothouses has been the very 

 reverse of this. High night-temperatures have 

 been kept up by the most unnatural of all 

 means — namely, fire-heat ; a forced and unna- 

 tural excitement has been imposed upon plants, 

 and the consequences have been more or less 

 fatal to them, in nearly the exact proportion to 

 which this fallacious practice has been carried. 

 An obvious analogy exists between the differ- 

 ence of temperature during the day and night, 

 and that between summer and winter ; the for- 

 mer may not inaptly be regarded as one long 

 day, and the latter as a night of similar dura- 

 tion. During the former period, abounding with 

 VOL. II. 



light and heat, vegetation is pushed on to its 

 fullest extent, declining as autumn advances, 

 and as light and heat decrease, until winter 

 nearly, but not entirely, arrests the vital action 

 of vegetation. During winter, the vital action 

 of plants ceases not entirely, but is only reduced 

 in intensity. " The roots continue to absorb 

 from the soil food, which is slowly impelled into 

 the system, whence it finds no exit ; it there- 

 fore gradually accumulates, and in the course 

 of time refills all those parts which the previous 

 season's expenditure had emptied. In the 

 meanwhile the excitability of the plant is re- 

 covered by rest, and may be even conceived to 

 accumulate with the food that the absorbent 

 system of the roots is storing up. At length, 

 when the temperature of the season has reached 

 the requisite amount, excitability is once more 

 aroused, an abundance of liquid food is ready to 

 maintain it, and growth recommences, rapidly 

 or slowly in proportion to the amount of excite- 

 ment, to the length of previous repose, and to 

 the quantity of food which had been accumu- 

 lated."— TA^ory of Hort., p. 92. 



A series of experiments on the progress of 

 the growth of plants during night and day was 

 made some years ago in the garden of the Hor- 

 ticultural Society of London, and the follow- 

 ing results appear. The supposed average of 

 the night temperature to which they were ex- 

 posed was 69°, and the following is the rate of 

 growth in inches : — 



Fig, 



Willow, . 

 Paasion flower. 

 Vine, 



Hight. Eay. 



9.60 9.92 



19.08 21.65 



36.20 35.85 



34.15 31.4S 



99.03 



101.77 



From this it appears that they grew as fast by 

 night as by day, because they were unnaturally 

 stimulated, for the apparent difference is obvi- 

 ously unimportant. A different result followed 

 growing these and other plants in the open air, 

 and fully exposed to the cold night- temperature 

 of England, as the following table will show: — 



102.33 289.49 



In carrying out this latter experiment during 

 a part of another month, the total growth by 

 night showed 119.07, and by day 337.16, show- 

 ing the natural growth of plants to be, during 

 the night, only 1 inch, while during the day it 

 was 3 inches; while by bad artificial treatment, 

 as will be seen from the first table, their growth 

 was equal during both day and night. " The 

 inevitable consequences of this inversion of na- 

 tural growth is immature or unripe wood, with 

 imperfect ill-constructed buds and a feeble con- 

 stitution, entirely incapable of bearing the shock 

 of great falls of temperature. More espeoiallyi 



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