discoveries which have rewarded patient research. The fine powder or pollen needs to be carried to the seed, so that its properties may operate upon that seed, if it is to be fertilized, or so matured, as to fulfil its function in generating a new plant when it is committed to the soil. In many cases it is enough that the fine powder should fall down from its elevation on the seeds below. This is self-fertilization, and is easily provided for by the mere bending of the head of the flower as it approaches maturity, or by the swaying of it in the breeze. But a more difficult, and as we might be inclined to add, more precarious, because less certain, method for fertilization is required in many cases. The experiments carried on by all our gardeners, and in a still more extended scale in all our centres of botanic research, have established the fact that in many cases, the yellow powder of one plant must be in some manner carried over to the seed produced within another flower, if that seed is to yield a satisfactory result to the horticulturist. We have thus two prominent facts here. The one is _the essential importance of the pollen_ for fertilization; and the other, _the need for the transference of the pollen_ from one plant to another in order to secure reproduction of vigorous growth by the sowing of the seed. As to the first, the pollen, which appears a fine powder or flour contains fluid protoplasm, that which Professor Huxley has described as the "single physical basis of life under all the diversities of vital existence."[BR] These pollen grains falling on the seed discharge their protoplasmic fluid upon it, and by this means contribute to fertilization. This original or primordial form of vitalising agency is carried from one part of the flower to another, and this transference is the law regulating the propagation of flowering plants.