Temperature

TEMPERATURE. The question of temper ature has been somewhat treated of in the articles Earth, Germination, 'Meteorology and Soil. Itis an important subject, for upon temperature, as one of the prime factors, rests the question of the proper ripening of crops. Thus soils, exposed to the rays of the sun, have varying powers of absorbing warmth and holding heat, as a rule, those which absorb fastest, soonest give it up. To ripen the cereal crops an average tempera ture of 56° Fahr. is required. Yet this rule is not a constant one, for in the Red river country, west of lake Superior, in latitude 50°, the mean annual temperature is 32°, and yet in consequence of a clear tropical heat of sixty days, wheat and other valuable cereals are ripened. So we can not take the establishment of a general rule as correct, for the decrease of temperature as we proceed north, as indicating the climate that may be expected. In central Europe, the change in mean annual temperature is said to be a lower ing of the temperature of one degree for every seventy miles of northing. In the TJnited States, in the valley of the Mississippi, it is reported as. one degree for every forty miles. Yet in the. valley of the Mississippi, in consequence of the great and continued heat of summer, certain crops are ripened perfectly, that can not be ripened in a corresponding latitude in central: Europe; but, again, certain crops, as grapes, are ripened as to particular varieties, in Europe, that can not be in a corresponding latitude in the United States. In the planting of crops where special earliness is desired, sandy soils are recog nized for their value. Drying easily in the spring, they consume heat, as can not be expected in dark, peaty or stiff clay soils. So the protection. of hedges, wind breaks, fences and glass struc tures are resorted to, to increase and conserve the heat of the sun. Thus the temperature is raised during the day to 70 and 80 degrees in the months of March and April and conserved dur ing the night, through the prevention of radia tion, by means of the covering, and by the aid of bottom heat. Thus all the more tender plants such as cucumbers, tomatoes, peppers, egg plant, etc., are forced. The heat to which the soil is often raised by the sun's rays alone is but little understood by the people generally. The range favorable to vegetation is from 34° Fahren heit to 140°, in like manner, too, the very ger mination or first vital action of the seed must have between 34° and 40°, so that there be no danger of decomposition, and sufficient warmth to maintain circulation. The common pea, requires at least 40°, and when it is forced for early use the temperature is from 45° to 50° ;. that of the air to keep it growing healthily is at 60°, and after it has flowered from 52° to 70° is necessary to mature its pods. An ordinaiy green house, which contains a miscellaneous collection) of hardy plants and shrubs flowering in the winter months, may be regulated to advantage, if its temperature be not lower than 45°, but by the sun's rays in the day-time it may rise to 65°, or even higher, to fall again to 45°, or a little below. The cooler temperature of the night time is favorable to all plants, inviting them to repose, by diminishing their excitability. Prof. James F. W. Johnston, in one of his lectures on the general relations of science to practical agri culture. delivered before the New York State agricultural society, states that, in this country, the temperature of the earth, five feet below the surface may be warmed by the sun to 100° and_ a half an inch below the surface sometimes rises as high as 140° Fahr. Such statements seem scarcely credible; yet, according to Dr. Coulter, plants grow on the banks of the Rio Colorado. which occasionally endure this intense heat. Sir John Herschel found the soil in his bulb garden at Cape Good Hope, on the 5th of December. 1837, between 1 and 2 o'clock p. raised to 159' of heat, and at 3 o'clock p. m., it was 150', and even in shaded places 119°. The temperature of the atmosphere in the shade in the same garden at the same period was 98° and 92° Fahr. At 5 o'clock p. m. the soil of the. garden, having been long shaded, was found to have, at four inches in depth, a temperature of 102°. On the 3d of December, a thermometer was hurled a quarter of an inch deep, in contact with a seedling fir of the year's planting, quite healthy, and having its seed leaves, marked a S follows: at twenty-five minutes past 11 o'clock a. , 148.2 ; at forty-eight minutes past 12

rn., 149.5' ; at thirty-four minutes past. 1 p. in.. 149.8'; at tifty-four minutes past 1 p. m., 150.8' ; and at forty-six minutes past 2 o'clock p. m., 148' Fahr. Similar statements were made by Prof. William Henry Harvey, in lus lectures on botany before the Lowell Institute, at Boston Massachusetts, in 1849, when he also stated that desiccation of the soil in consequence was so great that severe labor was requisite to lift the bulbs of the amaryllis, gladiolus, and kindred genera from the earth, and that each year's successive decay of leaves formed an envelope around the bulbs which served as pro tection, and preserved their vegetative powers. Front accidental circumstances it has been proved that a similar drying process will not injure the gladiolus in cultivation, but rather seems to serve as a stimulus to activity on appli cation of moisture. Gardeners have long resorted to similar expedients to induce certain succulent plants to flower, by delaying their seasons of repose and rest by heat and dryness. Such well observed facts confirmed the previous statements of Bruce, that the temperature in the sun at Gondar has been a,s high as 113' ; at Benares, 110', 113°, 118', according to Harvey; and at Sierra Leone, 138°, according to Winter bottom. In the relation of heat to germination there is a lowest and a highest point, and also a temperature of most rapid germination. This latter is about ten degrees greater, than half the sum of the lowest and the highest temperature of germination and the temperature of healthy germination about ten degrees above the lowest temperature of germination. The range of temperature for agricultural plants in the north, to ensure active and healthy germination, may be stated to be at about 55° for the more hardy to 90' for the most tender. Goppert found no seeds of plants, usually sown, to ger minate below 39', and Sachs gives the lowest temperature at from 41° to 55', and the highest range at from 102' to 116° So also he found the point of most rapid germination to be between 79= and 93° of temperature. There are, of course, some plants that germinate at a very low temperature and others that require a much higher one. Some arctic. plants germi nate when the temperature stands at or exceeds thirty-two degrees, and the cocoanut is said to germinate certainly- only when the heat of the soil is 120 degrees. What we have been indicat ing, relates to plants cultivated in temperate and sub-tropical climates. The following table will elucidate our meaning, as showing temperatures of germination: With wheat may really be placed all the cereal grains, peas, and all hardy vegetables, as radish, parsnip, turnip, lettuce, etc. With Indian corn all that class which actual freezing will destroy, including all the dwarf beans. With the squash may be included all the more tender plants, in cluding lima and other running beans, tomatoes, egg plants, etc. Among the cereal grains oats, perhaps, should be excepted. Oats should rather he placed with the pea, and with this, or rather hetween this class, and Indian corn, all the half hardy plants, as flax, Hungarian grass, celery, beets, onions, etc. Potatoes are susceptible to frost. They require about tbe same temperature for germination as Indian corn, but they may be planted very early in the season, since until the ground gets warm, germination goes on so slow that they do not appear above ground until all danger of frost is generally over, and if the soil be not sodden with water they will not decay. So, also, the seeds of any grain if.sown early, and not exposed to become water-soaked in the soil, they will germinate when the proper ten) perature is reached, and growing, will be more hardy than when they sprout more quicicly after being sown. Thus Haberlandt found that with a temperature of forty-one degrees, rye formed rootlets in four days, the other cereals and clover in from five to seven days, and at fifty one degrees the time was shortened one half. At this latter temperature kidney beans required eight, Indian corn eleven, and tobacco thirty-one days to com mence active germination. At sixty-five degrees the cereal grains, clover, flax, and peas, begin to sprout in oue or two days; beans, corn, and sugar beets in three days, and tobacco in six days. (See articles Heat, Light, Electricity, Germina tion, etc.