average of ten years there is no appreciable difference between the results. Duration, in days, from sowing to heading of winter wheat, at Montsouris, France. Date of sowing. 1872. 1873. 1874. 1875. 1876. 1877. 1878. 1879. 1880. 1881. 1882. This table shows that on the average of ten years the seed that was sown, e. g., on the 27th of October and required one hundred and fifty-five days to head, is that which took the longest time; for sowings before that date, as well as after it, the durations steadily diminish; in other words, this sowing is that whose development was the most retarded by the winter cold. If we compare this table with those given by Marié-Davy, showing the frosts, we find a complete inversion in the chances of injury from frost; wheat as a green plant has as little to fear from frost as has the dry grain. But during and after the formation of the embryo seed, as well as during germination, on the contrary, frost is very injurious, and if the embryo is seized by frost it perishes. If this accident occurs it is possible that the progress of heading may permit a new formation of embryo to replace those which have perished. Such accidents must have occurred to the seed sown in the hope of reaping an early harvest in 1874, 1875, 1876, 1877, 1878, and 1881, but did not occur in 1882. This accident is not incompatible with an excellent harvest, as we see in the case of 1874, but it causes a decided retardation of the harvest, as in 1877. The mean of the ten years shows that the heading occurs at an epoch in the spring when the mean temperature of the air is between 6° and 13° C., and when the rainfall is generally abundant, so that at this epoch damage does not generally occur to the grain; only in case of the sowing of September 29, 1878, did the heading occur during the very cold season likely to be injurious to vegetation. We pass now to the period from the heading of the wheat to the flowering. According to the determination of Herve Mangon, the sum total of the mean daily air temperatures in the shade necessary to flowering is 1,500° C., counting from the date of sowing, or 860° if counted from the date of heading. If we consider the date thus fixed for the flowering we shall find that it corresponds to a mean daily temperature at that epoch of 16.5° C. on the average of many years; but if we consider the individual years we shall find the actual mean temperatures of that date to vary from 8° to 22° C., and also that for temperatures below 13° the flowering becomes uncertain, prolonged, and detrimental to the crop; but as to the upper limit, 22° C., there is no evidence that even higher temperatures will be injurious. The following table gives the calculated number of days that elapse from the sowing to the flowering, together with the average duration and the corresponding average date. The corresponding tables of mean temperatures and lowest temperatures at the date and the quantity of rainfall are omitted for want of space. Duration in days from the sowing to the flowering of winter wheat at Montsouris, France. Average for 1872-1881. Date of sowing. 1872. 1873. 1874. 1875. 1876. 1877. 1878. 1879. 1880. 1881. 1882. October 6 October 13 241 October 20 238 225 231 October 27 232 September 22... 244 228 239 237 238 208 231 261 242 235 239 236 May 16 239 236 May 23 235 236 231 232 249 234 229 225 The ripening of wheat is perfected when the plant has received a sun, total of mean daily air temperatures in the shade of 815° C. since the date of flowering. This result happens on the average of Paris forty-four days after flowering, and the individual irregularities scarcely ever exceed four or five days. Therefore the date of flower ing can be made the basis of a very close estimate of the date of ripening. The date of flowering occurs at the time of the greatest vital activity of the plant, which at that time is actively drawing its nourishment from the soil and is transpiring, assimilating, and increasing in weight. But very soon this work is relaxed and is confined more and more to the interior of the plant, conveying into the seed the elaborated materials formed within the leaves and stems. It is especially in this latter part of the life of the plant that the internal consumption can exceed the gain from without, and the plant tends to diminish its dry weight. This period has a great influence on the final result, not only because the plant can gain as a whole, but especially because of the distribution which is made within it of the material which it has brought together. The straw has only a secondary value. It is the seed which constitutes nearly the whole value of the harvest. Therefore all that passes from the straw to the grain is a benefit, though this passage should be accompanied by a notable consumption of the nutritious materials of the stalk. It is neither the state of preparation of the stalk, nor the heat, nor the radiation, nor the moisture which of itself alone produces the best quality of grain. There must be a reunion of all these various elements in a proper proportion, which latter will vary with the weather and with the locality even with the same weather. The blighting of wheat is an accident that one dreads. most at this period. The blight, properly so called, is due to a temperature and a radiation that is too intense for the movement of the sap in the plant; the seed has not time to receive the sum total of the nourishing particles that have been prepared for it; therefore it becomes small, lean, and shriveled up. A greater sum total of moisture in the soil or a less active transpiration would have given a better result. But we often confound the blight, properly so called, with the analogous result produced by an insufficient assimilation or elaboration of the various materials that go to make up the wheat grain or by a disproportion in the relative quantities of the elements that should make up the seed. The following table shows the number of days elapsing from sowing to ripening for the dates adopted in the previous tables. It is calculated by first ascertaining the number of days elapsing from flowering to ripening according to the rule above given and then adding these intervals to those already calculated for the flowering. Duration, in days, from sowing to ripening, for winter wheat at Montsouris, France. Average for 1872-1881. Date of sowing. 1872. 1873. 1874. 1875. 1876. 1877. 1878. 1879. 1880. 1881. 1882. September 22... 291 282 284 285 287 268 281 311 292 285 290 287 July 6 In the following table I present a summary of the preceding details, showing the average duration and dates for the ten years from 1872 to 1881, inclusive. To this I have added the average total daily radiation for crops sown in 1873 to 1880, as computed by Marié-Davy in actinometric degrees for two phases, viz, from heading to flowering, and for thirty days after flowering, which brings us through the greater and more important part of the ripening phase. Summary of dates and radiation for winter wheat during ten years, 1872-1881, at Montsouris, France. Summary of dates and radiation for winter wheat during ten years, 1872-1881, at Montsouris, France-Continued. On the average the wheat sown October 13 and ripening July 19 received the most sunshine during the last two stages and should give the best crop. The preceding study gives the details of the weather and the development of the wheat from 1872 to 1882. Marié-Davy compares these figures with the annual reports of the total crops actually gathered in the Department of Seine-et-Oise, immediately surrounding Montsouris, as shown in the following table, assuming that the crop ripened at any time between July 6 and August 7 during those years. Wheat crops and sunshine at Montsouris. If we summarize the five years of crops above the mean and the four years of crops below the average, as indicated in the preceding |