We find that vegetables have long spindling shoots, and wide spaces between the leaves or buds, when growing in a damp, still, close atmosphere, especially when the plant is sickly or weak from deficiency of nourishment, and that this happens equally, whether a trailing plant being supported aloft throws out depending shoots in opposition to the current of light; whether a climbing[52] plant runs out horizontally along a branch or beam at right angles to the light, or whether a self-supported mounting plant rises in direct opposition to gravity. No doubt, when the light comes from one direction, {271} such as the aperture of a window, the plant shoots forth towards the light, possibly in consequence of the leaves inclining themselves to receive the ray on their superficies, and thus leading the shoot in the direction of the light. But this does not prove any straining or lengthening of the shoot to approach the light; and we ask, what do general opinion and Sir Henry found their belief upon, of lengthening growth and straining to approach the light? Again, with regard to heat, we notice that plants, particularly shoots from tubers, left to sprout in cold, damp, confined cellars, throw out very long stems, with wide spaces between the buds or leaves, and that very long shoots always occur in confined damp air—long in the ratio of the dampness and confinement, whatever the degree of heat may be, provided it exceed a little the vegetating point. Also on the north side of hills, the trees have generally longer stems than on the sun-ward side, although in the former case, they are exposed to the northern blast, while in the latter they bask in the sun. Has the same kind of plant, in lower latitudes, longer spaces between the leaves than in higher? And if it has not, is the cold, from greater evaporation, sufficient to balance the superior heat of the climate? {272} The above facts must lead, we think, to the conclusion, that evaporation, or non-evaporation, of the fluids, has, directly, a very considerable influence in causing a shorter or longer extension of the shoot between the buds or leaves, and that the influence of the cold of this evaporation is at most but of a very secondary character. We would compare the extending rudiments and matter of the young scion to the slow flowing of a gelatinous fluid. In moist air, the watery part is slowly evaporated, and the drop extends into a long pendulous form. In dry air, the water of solution is quickly evaporated, longitudinal extension ceases, and the pendant is thicker and shorter. The cold of evaporation may a little affect the fluidity, but only in a very small degree[53].