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Data, by pentads, for Montsouris, 1889, as published by Descroix or specially computed—Continued.

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THE RESULTS OF RECENT STUDIES BY ANGOT.

In 1880 the Central Meteorological Bureau of France, under the minister of public instruction, organized a system of phenological observations; the resulting data have been studied by Angot in a series of memoirs.

In his first paper (1882) Angot grouped the dates of the wheat harvest as observed during 1880 and 1881 at several hundred stations in France in groups of four or five stations and plotted these upon maps showing the elevations of the stations. By a careful comparison of neighboring stations he shows that the date of the harvest is everywhere quite uniformly retarded with increase of elevation, and at the rate of four days in time for every hundred meters of ascent. Apparently this retardation is the general result of a complex system of influences in which rainfall, drainage, soil, sunshine, temperature, and other local peculiarities combine. It is evident that the special influence of any local climate on the crop can not be successfully studied until the observations have been corrected for the general influence of elevation. He therefore reduces all the dates of harvest to sea level by applying the preceding correction.

A similar calculation showed him that the phenomena of flowering are also retarded at precisely the same rate of four days per 100 meters of elevation and these dates also are thus reducible to sea level.

Angot's charts, showing the dates of flowering and harvesting thus reduced to sea level, show great regularity and the isanthesic lines show the perfect regularity with which the reduced epoch of flowering begins in southern France on the 11th of May and advances northward until it reaches the northern boundary of France on the 25th of June; in a similar way the harvesting of winter wheat begins in southern France on the 10th of June (reduced epoch) and in northern France on the 9th of August. The variations of these isanthesic lines from year to year may be compared with the ordinary charts of temperature reduced to sea level or with other meteorological data in a very simple manner.

Angot has modified and apparently improved the methods of determining the influence of temperature on the date of flowering and harvesting. He says that since 1837 Boussingault's idea that the ripening demands a certain sum total of heat, which is constant for each species of plant, has been generally adopted. At first this sum total was calculated by adding together all mean daily temperatures from the germination of the seed or the beginning of vegetation after rejecting such means as were below freezing point.. Then, as C. H. Martins, De Gasparin, and A. de Candolle had shown

that the temperatures useful to the plant vary with the species and are decidedly above freezing, therefore students have taken other limits. Thus Gasparin and Hervé Mangon adopt 6° C. for the initial temperature in the growth of wheat. In order to ascertain the proper method of counting temperatures Angot has accomplished the labor of prosecuting three parallel computations by three different methods, as follows:

(A) First method.-By observations of daily maximum and minimum temperatures. In this method Angot has examined separately the observed maxima and minima of the thermometer in the shade. After rejecting all observations below 6° C., he subtracts 6° C. from all the others and takes the separate sums of the remaining maxima and minima for each month and then the average of these two sums, which consequently represents a sum total of heat received during the month in excess of 6° C.

(B) Second method.-By the daily means. In this method the mean of each day is first computed by taking the average of the maximum and minimum; 6° C. is then subtracted from each of these daily means and all negative remainders are rejected. The sum of the positive remainders represents the sum total of heat received in excess of 6° C.

(C) Third method.-By maximum temperatures alone. In this method, which is a modification of that proposed by Hoffmann, a maximum thermometer is exposed to the direct rays of the sun and the sum total of the maximum temperatures is used by Hoffmann. But Angot prefers to use the maximum thermometer in the shade, as in the first method, and, as before, takes the sum total of all the positive remainders after subtracting 6° C.

In all these methods the principal difficulty is to fix the epoch from which the summation should begin. Sometimes the date of sowing has been adopted as this epoch, but from the date of sowing up to the date of sprouting the seed and the young plant are subjected only to the temperature of the soil, and not to that of the air, which often differ considerably. It would perhaps be better to start with the date at which the plant appears above the earth, but the date of sprouting is not generally given by observers. He therefore provisionally adopts the 1st of December as the point of departure and calculates the sum total of temperatures for the nine stations in France for which the dates of flowering and harvesting of winter wheat have been best determined for the years 1880 and 1881. The agreement among themselves of the numbers calculated by these three methods for nine stations and two different years is such that no decision can be arrived at as to which method is the best, and such decision is reserved for a future study of other harvests.

A similar elaborate study of the harvest of rye gave the following results:

(1) Retardation for altitude is approximately four days per 100 meters, with some indication that the correct figure is rather less than this.

(2) The date of harvest reduced to sea level begins with the 5th of June in southern France and ends with the 25th of July on the northern border.

(3) The sum total of temperatures computed by the three methods A, B, C, above mentioned, shows that whatever method be finally adopted as the best, these sums are less for rye than for winter wheat.

A similar study for spring barley shows the following results: ́ (1) A retardation of four days per 100 meters of altitude sufficiently harmonizes the observations.

(2) A retardation of thirty or forty days in the date of sowing has no appreciable effect on the date of harvest, which varies from the 20th of June in southern France to the 14th of August on the northern boundary.

(3) The sum total of temperatures from sowing to harvest is too variable to be determined.

A similar study of the flowering of the narcissus (Narcissus pseudonarcissus) shows that the retardation of the date of flowering is at the rate of four to five days per 100 meters, and four days can be adopted without notable error.

A study of the currant (Ribes rubrum) shows that the retardation is between three and four days per 100 meters. The sum total of heat from December 1 up to the date of flowering, as deduced by the second and third methods, but under three different assumptionsi. e., that the initial temperature is 4°, 6°, 8°, respectively, seems to show that 4 is the proper figure for this plant.

A study of the flowering of the lilac shows that a retardation of four days per 100 meters best satisfies the observations of both leafing and flowering. The latter begins in southern France on the 22d of March and ends in northern and eastern France on the 6th of May. The calculation of the heat required for leafing shows that the most accordant results are obtained when we take the sum of maximum daily temperatures above 4° C. and count from the date of the last heavy frost, which sum is about 360° C. For the flowering, on the contrary, we have to take the sums of the mean daily temperatures, counting from 4° C. and from the same date of frost, which sum is then 350° C., while the sum of the maximum daily temperatures would have given 695° C.

A study of the leafing and flowering of the horse-chestnut (Esculus hippocastanum) shows that the retardation of four days per 100 meters also satisfies these observations. The dates of leafing, as

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