Too much moisture prevailing at the time of the blossoming of our fruits, especially moisture precipitated in the form of rain during this period, is sometimes disastrous to our crops, both of cereals and of orchard fruits. Continuous showers prevent the development of the pollen-grains, and their transfer to the stigmas of the blossoms, so that the fruit does not set well. Fortunately this does not often occur in our glorious climate, which is so highly favored by an abundance of light and sunshine, which are the great and essential stimuli of the higher orders of plants. The loss of our fruit crops in some parts of the Ohio Valley in the years 1862, 1865, and 1866, was fairly attributed to this cause. We must not overlook the unhealthy influences produced by an excess of moisture in the earth. Many plants that naturally delight in a dry porous soil, become weak, unfruitful, or even seriously diseased when they are planted in low wet grounds, or upon such as are underlaid by a very tenacious sub-soil, while an opposite condition is equally unfavorably to those that are naturally more aquatic in their tastes and habits. In the former case we learn to avoid such soils and situations, unless we are able to change their character in this respect by thorough under-draining, which will completely remove the evil, and the remedy becomes merely a question of expense. A certain amount of temperature may be assumed as requisite to every plant, or rather it may be affirmed that some plants cannot exist and thrive except within a certain range, and it has been asserted that each class of plants requires a mean temperature for the year that shall not vary many degrees: the range of this variation has perhaps never been satisfactorily ascertained. But it is well known, that both heat and frost act injuriously upon vegetation. Mr. Lindley tells us that "the extreme limits of temperature which vegetables are capable of bearing, without destruction of their vitality, have not been determined with precision." When the temperature is maintained at a higher point than is natural, the plant is excited to undue activity of growth; but this is attended with an enfeebled condition, often seen in badly managed green-houses. Mr. Knight found that certain plants were rendered abortive by the production of male flowers only, when exposed to too great heat, and by an opposite treatment, when subjected to a low temperature for a long time, others produced only female flowers. In some plants a high degree of heat, with moisture, results in the production of leaves only, and Humboldt found that wheat was grown about Xalapa, Mexico, as a fodder plant, because it produced an abundance of grass, but did not form ears nor grain.