Page:An introduction to physiological and systematical botany (1st edition).djvu/129

 Rh power of seeds, nor do we know any degree of cold that has such an effect. Those who convey seeds from distant countries, should be instructed to keep them dry; for if they receive any damp sufficient to cause an attempt at vegetation, they necessarily die, because the process cannot, as they are situated, go on. If, therefore, they are not exposed to so great an artificial heat as might change the nature of their oily juices, they can scarcely, according to the experience of Mr. Salisbury, be kept in too warm a place. By the preservation of many seeds so long under ground, it seems that long-continued moisture is not in itself fatal to their living powers; neither does it cause their premature germination, unless accompanied by some action of the air.

It is usual with gardeners to keep Melon and Cucumber seeds for a few years, in order that the future plants may grow less luxuriantly, and be more abundant in blossoms and fruit. Dr. Darwin accounts for this from the damage which the cotyledons may receive from keeping, by which their power of nourishing the infant plant, at its first