served can also be accounted for by attributing them to certain differences in the atmospheric conditions.

(6) The more considerable absorption of oxygen by seeds under the influence of light explains the fact that asparagine (the medium for the conveyance of the reserved albuminous substances in the germination of leguminous plants) only disappears in plants exposed to the light and continues present in those raised in the dark. The comparative researches of Pfeffer (1872) upon the chemical composition of asparagine and other substances showed that asparagine is poorer in carbon and in hydrogen and richer in oxygen than legumine and other albuminoids. The transformation of legumine into asparagine is accompanied by the absorption of a certain quantity of oxygen. On the other hand, it is effected only by the influence of light, the reason being that light increases the quantity of oxygen absorbed, and therefore exerts only an indirect influence on this change, as had already been surmised even when we were not acquainted with the reasons.

(7) Other new and important conclusions become apparent from these experiments and those which follow, and although they have no direct connection with the subject of my work I think it will be well to designate them briefly.

The quantity of oxygen absorbed in a certain space of time by a seed in process of germination varies very considerably according to the temperature; it increases with it, as has been already proved in treating of the respiration of plants in the dark. The general results of my experiments, and particularly of Nos. 9 and 10, leave no doubt of this fact. We can therefore easily understand what errors have been committed by those experimentalists who have given calculations of this absorption of oxygen by certain seeds without taking into consideration the conditions as to temperature. Their figures have no value whatever, particularly in view of a fact stated by me several times already, viz, that the quantity of oxygen absorbed by a seed is not at all in proportion to its apparent development, but, on the contrary, undergoes considerable variation, depending upon the influence of the external agents affecting the phenomenon. Accord ing to my observations, this quantity may vary as two to one, or even more, in two plants of identically the same weight, but placed in different thermic conditions from the commencement of their germination to the emerging of the rootlet. From this point of view, then, the plant acts like a complete organism, its respiratory action being accelerated or retarded always, however, within physiological limits, like those of an animal under the influence of certain exterior changes.

Having thus shown that germinating seeds absorb more oxygen in the light than in darkness, Pauchon conducted some experiments to determine the ratio between the oxygen and the carbonic acid, and draws the following conclusions (see page 182 of his work):

Experiments Nos. 3 and 4 have a real value for the solution of the problem brought forward in this part of my work. As to the partial results given by experiments Nos. 1, 2, and 5, their accuracy can not be doubted; therefore I shall make use of them as confirmatory documents. I must repeat that the numbers used for the proportions of

2667-05 M- 4

the quantity of oxygen absorbed and the amount of carbonic acid exhaled by a plant placed in the light and under natural conditions, it will easily be understood why we refrain from making any comparison until we are in possession of all the data necessary to carry out the calculation.

(9) The facts which precede convince me that the seeds of uncultivated plants germinating in the light are, all other conditions being equal, better distributed than the seeds of cultivated plants; that they possess a greater germinating power, an advantage which increases their chances for ulterior development.

Chapter III.

THE TEMPERATURE OF THE SOIL.

OBSERVATIONS AT HOUGHTON FARM AND GENEVA, N. Y.,
D. P. PENHALLOW.

BY

In reference to the value of soil temperatures, Penhallow states (Agr. Sci., Vol. I, p. 78):

A proper knowledge of the temperature of the soil must serve to guide us in reference to the time of planting particular seeds and the depth at which they should be planted, as determined by the condition and character of the soil. When the farmer gently packs the earth over the planted seed he derives a measure of benefit in the higher temperature of the soil at that place, whereby germination is accelerated. Similarly, we can understand that cultivation during periods of excessive heat must tend to avert some of the evil results otherwise following from an excess of temperature. Moreover, in seasons of great or even of ordinary dryness a judicious system of irrigation must be of the greatest advantage, not only as supplying needed fluids for the general functions of growth, but as reducing the otherwise high temperature of the soil to a degree that is well within the danger limit and consistent with normal growth.

Penhallow also shows from observations at Houghton Farm and at Geneva, N. Y., that all layers of the soil within 3 inches of the surface have temperatures that depend not merely upon absorption of solar heat but also upon the cooling due to radiation and evaporation. The depression due to evaporation amounts to about 8° C. on the average of the warmer half of the year and is even more than this when hot days and strong dry winds produce an excessive evaporation.

OBSERVATIONS BY E. S. GOFF.

E. S. Goff adduces observations to show that the temperature of the water at the time when it enters into the roots from the soil has some relation to the temperature of the stem of the plant for a short distance above the surface soil, and that the distance up the stem to which this temperature is felt depends upon the rapidity of the flow of the sap, and therefore ultimately on the rapidity of transpiration from the leaves. (Agr. Sci., Vol. I, p. 134.)

OBSERVATIONS OF TEMPERATURE OF MANURED SOILS IN JAPAN BY GEORGESON.

Soil temperature must to some extent be affected by the heat given out by decaying manure and vegetation. On this subject Mr. C. C. Georgeson describes some experiments being made at Tokyo, Japan (Agr. Sci., Vol. I, p. 251), from which it appears that the temperature immediately after applying the manure was from 2° to 5° F. higher than in the unmanured soil, and this excess steadily diminished, but was still appreciable at the end of two months. The 2° of excess occurred when the manure was applied at the rate of 10 tons per acre, and the 5° of excess when applied at a rate of 80 tons per acre.

INFLUENCE OF RAIN ON

TEMPERATURE
MUNICH. (K. SINGER.)

OF THE SOIL AT

The study of the earth temperatures at considerable depths is a problem for terrestrial physics, but for agricultural purposes we need only consider the temperature of the soil within 4 or at most 8 feet. The work of Karl Singer (1890) is sufficiently instructive to justify the presentation of his general results for use in studying the phænological phenomena of Europe. In a simple diagram Singer summarizes at a glance the mean temperature of the soil at any depth between 1 and 7 meters for any day of the year, as it results from an average of thirty years of observations at the observatory at Bogenhausen, near Munich, Bavaria. The series of observations includes, in fact, four sets of earth thermometers, two of which were on the northwest side of the observatory and the other two on the southeast side; the diagram and the following summary of results relate to the average of the pair on the southeast side. Each set of thermometers consisted of five, whose bulbs were buried at depths of 4, 8, 12, 16, and 20 Bavarian feet, respectively, or 1.2, 2.4, 3.6, 4.8, and 5.9 meters, respectively. The lines given in this diagram are thermal isopleths, viz, curves of equal temperature for successive depths and days, the days being represented by vertical lines and the depths by the horizontal lines. The following paragraphs express the general results of Singer's work as far as it bears upon the growth of plants:

(1) The normal mean temperature of the earth for twenty-five years (1861-1885) at Bogenhausen, near Munich, at certain depths, is as follows:

(2) The mean temperature of the earth at a depth of about 1 meter below the surface exceeds the mean temperature of the air [at a meter above the surface] by more than 2°. The important influence of the considerable altitude above sea level of the place of observation is to be recognized in this result.

(3) The decrease of the annual amplitude with increasing depth for the adopted interval of 4 Bavarian feet, or 1.17 meters, amounts to 12.18° C., or very nearly one-third of the original amplitude of the atmospheric temperature. The amplitude AP in centigrade degrees at the depth P in meters is represented by log P=1.2620—— · 0.1508 P. Whence we compute the amplitudes given in the last column of the preceding table.

(4) The epoch of the occurrence of the extreme and mean temperatures for the highest thermometer, No. I, are: Minimum, 2d of March; first mean, 21st May; maximum, 24th August; second mean, 15th November. These are therefore separated from each other by intervals of about 23, 3, 23, 3 months, respectively. For each step downward of 4 feet, or 1.2 meters, in depth, the occurrence of the epoch of extreme temperature is retarded on an average 21 days and that of the mean temperature 24 days; therefore an almost uniform distribution of these dates is brought about down to a depth of 20.2 feet, or 6 meters, where the minimum occurs on the 23d of May, the first mean on the 24th August; the maximum 17th November, and the second mean on the 24th February.

(5) The actual temperatures of the ground from 1861 to 1889, at the upper stage of 4.2 feet, or 1.3 meters, or thermometer No. I, did not fall below 2° C. or rise above 17° C. At the lower levels they ranged between 4° and 14°, 5° and 13°, 6° and 12°, 7° and 11°, respectively.

(6) By a careful consideration of the state of the weather it is sible in every case to account for the connection between the fluctuations of the temperature of the air and that of the earth.

The following generalizations refer to the climate of the South Bavarian Plateau only and to the four seasons of the year:

(7) In mild and, as usual, rainy, winter months, there is no material rise in the temperature of the earth relative to the average temperature curves, particularly at great depths, but generally a lowering of temperature.