Page:Journal of botany, British and foreign, Volume 9 (1871).djvu/184

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162 SUGAR IN BEET-ROOT.

But this series of sugar-estimations was too imperfect to admit of satis- factory conclusions being drawn from it. So, in 1870, another and far more complete series of observations Avas made. The soil was analysed and the rainfall and temperature regularly recorded, while the determina- tions of sugar, commenced in August, were continued at fortnightly inter- vals, until December. The weight of the plants taken up for analysis at each successive period, was also noted, with the proportion of root to leaf which they showed. I do not propose to give liere all these details of the experiments, but to confiue my remarks to the main conditions affecting the production of sugar in the root.

The table prefixed to this note (Plate CXVII.) represents the rainfall during, and the percentage of sugar after, a series of fortnightly periods. Before making a few remarks on the " sugar-curve," I present, in the annexed table, some of the chief data of the experiments: —

Sugar in Beet-root, 1870.

Periods.

I. July 28 to Aug. 9. II. Aug. 10 to „ 23.

III. „ 24 to Sept. 6.

IV. Sept. 7 to „ 20. V. „ 21 to Oct. 4.

VI. Oct. 5 to „ 18.

VII. „ 19 to Nov. 1.

VIII. Nov. 2 to ,,1.5.

IX. „ IG to „ 29.

It should be added that the average weiglit of the roots increased regu- larly and to a considerable extent at first, in periods I., II., and III.; afterwards, the increase was less regular. The temperature of the season had attained its maximum three weeks before Aug. 9th, and after that date decreased pretty steadily.

The most obvious conclusions to be drawn from the above table are the following: —

1. During root-development in August, and down to September 20th, the leaves do not proportionately increase, but present a relative diminu- tion of about one-third.

2. During the period referred to above, in I., the absolute quantity of siigar increases considerably, but, owing to the great increase in the abso- lute weight of the roots, its percentage proportion is only raised by about one-fifth of its percentage at the beginning of this period.

3. During October, the most rapid development of sugar takes place, the virtual maximum of the season being reached at the end of that month.

4. The fortnight without rain, ending Oct. 4th, was that in which the greatest increment in the percentage of sugar occun-ed (and, it may be added from other data, only an insignificant addition to the weight of the roots was made).

It is intended to continue these experiments, and to render them as complete as possible. It is hoped that important facts in the physiolo- gical chemistry of sugar may thus ultimately be learnt.

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