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Under such circumstances it is not surprising that the development of the crop of grain keeps pace with the increase of the available water, at least up to the point where the quantity of water is sufficient to give a maximum crop.

The supply of water has an influence not merely on the quantity of the crop, but also on the rapidity of the development of the plant. Wollny (1881) shows that in general the grain ripens sooner as the quantity of water diminishes. This is well seen in the following series of experiments (Table 62) on the time of ripening of grain in fields that are sown more or less thickly. The thickly sown fields correspond, of course, to a less quantity of water available for each plant.

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Similar experiments were made by Wollny on the Ramersdorfer variety of potatoes. A plat containing 1 plant to 4,435 square centimeters ripened by the end of September (1875), but a plat containing 1 plant to 812 square centimeters ripened the 1st of August, and other plats containing 1 plant to 2,500, 1,600, 1,109 square centimeters, respectively, ripened at dates proportional to the area occupied by each plant. As each plat received the same amount of sunshine and of water, the dates of ripening must have been hastened in proportion as the number of plants in each plat were increased.

MAIZE.

Similar experiments on maize showed a similar acceleration of the date of ripening, as given in the following table, which also shows in the last column what proportion of the maize was unripe in the sparsely planted plats when that which was closely planted was already fully ripe.

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A striking illustration of the effect of scant water supply is given in the case of four plats of flax, which were sown at the rate of 50, 100, 150, and 200 grams of seed per 4 square meters of ground. During the drought of 1875 the plants sown most closely all died early in July, whereas those sown most sparsely withstood the drought very well; of the plants sown with intermediate densities the number that died was proportional to the density. In general, if all other conditions are the same, plants ripen sooner and have a shorter duration of vegetation in proportion as the soil is drier, or in proportion as there are more plants to the unit area.

Evidently the plants whose roots extend the farthest in search of water will outlast the species or varieties whose roots are of smaller dimensions.

RAINFALL AND SUGAR BEETS.

Briem (1887) has investigated the effect of rainfall on the harvest of sugar beets. His observations were made at the experiment station "Gröbers." A long drought during August and September was followed by a rainy period of many weeks. During the latter the beets increased in weight on an average for each beet from 388 to 450 grams; the presence of sugar was shown by the ordinary polarization test, both before and during the rainy period. The following table gives the results of the analyses, each figure being the average of 16 readings on samples taken from 100 beets. These samples show that immediately after the first rainfall, on September 21, the percentage of sugar per beet diminished somewhat, but that toward the

end of the rainy period, when the rainfalls became less frequent, the percentage rose to nearly its former value. On the other hand there was a regular diminution of the other elements that were not sugar, and consequently an improvement in the percentage of purity. Therefore a permanent injurious influence of the heavy rainfall on the quality of the beet was not proven.

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Grassmann (1887) also confirms the results of Girard to the effect that the sugar once formed in the beet remains there, no matter what the further growth may be. There the diminution of the percentage of sugar after a rainfall is only relative in that the sugar is dissolved in more sap, and this is distributed throughout a greater mass of beet; the sugar, and with it the percentage of purity, sinks only very little after the first rainy day, but on the second sinks more considerably and then slowly rises from the third to the fifth day. (See Wollny, X, p. 300.)

REMARKS.

Now that the previous studies have shown the importance in agriculture of the quantity of available water the question still remains whether the results of these experiments are directly applicable to determining the influence of rainfall on vegetation under the natural climatic conditions. We could in advance answer this question in the negative, inasmuch as the precipitation is never so uniform as the water artificially supplied in these experiments, as also because the utilization of the natural rainfall by the earth varies with the physical properties of the latter; but by a closer consideration one is led to the conclusion that in spite of the departure from natural conditions still the results of these experiments do allow us to draw many conclusions as to the influence of rainfall on the growth of cultivated useful plants, especially when we leave out of consideration the effect of the water at different epochs of vegetation and the peculiarities of the capacity of the soil for water, and at first study only the average character of the climate as depending on the amount of precipitation and consider the weather during the growing season.

In this case it would scarcely be denied that a relatively dry or moist climate or any similar modification of the weather should exert an influence on the vegetation similar to that exerted by the soils of different moistures in the above-described experiments. We must the more readily agree to this conclusion since, independently of the fact that water belongs to the most important, indispensable factor of vegetation, it is also true that the observations on the growth of plants made in climates having different degrees of moisture agree closely with the views above explained. It is already well known in agriculture that in a dry climate the harvests are only scanty and to an extraordinary degree dependent on the rainfall, and, furthermore, it is well known how favorably the general condition of the plants is affected by a moderately moist climate, and how, on the other hand, the crops of cultivated lands are diminished by extremely large quantities of rain, when in consequence of a large capacity of the soil for water, a large quantity of water accumulates in it either temporarily or for long periods of time. Furthermore, it is well known that the stalk of the plants and the formation of straw are greater in proportion as the climate is moister; that the various kinds of cereals in dry regions produce a glassy, glutinous grain, but in moist lands a mealy seed, poor in nitrogenous compounds. All these phenomena, observed on a large scale in the life of the useful plants, make themselves felt also in a similar way in the experiments above quoted, and therefore the results of the latter can with perfect justice be quoted in deciding upon the questions lying at the base of our work. But these present conclusions hold good only for the total rainfall during the growing season, and it will be further necessary to fix in a similar way, by experiments, the influence of precipitation during the individual stages of growth of the plants, as also the relation of the soil to the water, so as to determine the influence of the ordinary natural climatic conditions.

Chapter VII.

MISCELLANEOUS RELATIONS.

RAPID THAWS.

The following extracts from a report for 1889 of the department of the interior of the Canadian government shows the influence of the change from warm to cold weather not only on forest trees but on other plants:

Considerable attention has been paid to this subject during the past year, and there has been urged on the department of agriculture the desirability of the establishment at some point in the southwestern portion of the Northwest Territories of a farm or garden for conducting experiments on this line. Failure in tree culture so far as tried seems to be owing not to the severity of the winters, nor to the droughts of the summers, but to the winds. Those in the winter known as 66 chinooks," which cause the sap to rise and the buds to swell, being followed by a lowering of the temperature (in some cases very rapid), prove destructive; and during the summer there are often high, dry, hot winds which blow continuously for several hours and which seem to dry up the young trees. By planting in close clumps the native trees which will grow (cottonwoods and others), and among them those ornamental trees which are so much to be desired, these difficulties will probably be overcome, and in time it will be found what ones are best suited to the district.

The great difficulty which at present impedes the cultivation of large plantations of forest trees in Manitoba and the northwest is climatic. In early spring, delightfully soft, balmy days, something like the maple-sugar weather in Ontario and Quebec, awaken the young trees to life and cause the sap to run; but then suddenly a terrific blizzard from the north and northwest comes down and freezes up the sap and destroys the trees. Professor Saunders is now engaged in experiments with a view to overcoming this climatic obstacle. I have thought that by planting the young trees very closely together, or by sheltering them during their earlier seasons, as is done in the case of the seedlings at the model farm at Ottawa, this trouble might be gradually lessened; or, willows or cottonwood might be planted with the young trees as a shelter-belt protection for them against these early spring frosts and sudden and extreme changes of temperature. As yet, of course, we have no practical experience in the northwest on the subject, and can only base any action we may take upon knowledge obtained from what has been

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