Temperature
A study of the ever-varying Temperatures daily experienced, and their effect on cultivated plants, forms an important part of the duties of every gardener who has under his charge anything beyond that which is of the hardiest description. Temperatures, it need scarcely be remarked, often fluctuate very suddenly from what is called one extreme to the other; and, as their guidance is beyond human control, it becomes a necessity on the part of cultivators to prevent such changes, so far as possible, from injuriously affecting plants, by giving constant attention, and anticipating what is likely to ensue. The degree of intensity of heat or cold is ascertained by the expansion or contraction of the mercury or spirit in a thermometer. From knowledge gained by experience, the extreme Temperatures that a large number of plants will withstand with impunity is often known, but there are exceptional cases where other conditions are unfavourable, and plants succumb in spite of all precautions. To know the Temperature in which various exotics succeed best, and the proper degree of heat requisite for bringing them to perfection, is one of the first essentials towards success. The maintenance of an equable Temperature in forcing operations, and in the culture of fruits under glass, is of great importance, as on it depends most materially the development of fruit or flowers, as the case may be. Forcing indoors is most intimately connected with, and dependent upon, the regulation of Temperature by means of the heating apparatus and the proper use of the ventilators when necessary. To know the country to which any given plant is indigenous, or to ascertain from a reliable source the degree of hardiness to which it may be subjected, is often a good guide in giving it proper treatment as regards the amount of heat required. But this is totally insufficient in dealing with the varied occupants of a large garden, and in conducting forcing operations in seasons when outside Temperatures often fluctuate very rapidly. Practical experience and unremitting attention are absolutely essential for good gardening, and, even when these are intelligently exercised in daily management, the operator finds there are many things beyond his control, sudden changes in the Temperature being amongst the most formidable.