This conservation of water on such a great scale offers striking contrast to the truly prodigal habits of certain plants that actually drip water, so charged are they with this precious liquid, and so little stress do their conditions of life put them under in this respect. Where water is plentiful and turgor maintained almost to the bursting point, evaporation in a moist or chilly atmosphere does not suck out water vapor fast enough. Sometimes, around the edges of the leaves of the common garden nasturtium, drops of water may be found, literally forced out as drops, rather than transpired as water vapor. This happens to a considerable number of plants, during the night when transpiration is laggard, and such drops are usually mistaken for dew. The latter is actually the condensation of moisture in the air upon the leaves of plants which cool down more rapidly than the air, and seldom due to the forcing out of drops of water from leaves, although in rare cases it may be. In tropical forests, where the humidity is very heavy and water supply from the roots copious, certain leaves leak water so fast and are so constructed that this excess is prevented from accumulating on the leaf. The pipal tree of India has long drip tips to its leaves that conduct the excess water from the blade to the end of the slender tip where it drips off. The advantage of these dripping points is obvious, for in regions so humid that water is forced out of the leaf, the coating of the leaf with this extra moisture would by that much retard transpiration. Dripping points, which in less exaggerated forms than in the pipal tree are common in many parts of the world, are thus of decided advantage. Whether it be desirous to retain water or to lose it by gradual evaporation, or expel an excess of it, each species of plant has developed the apparatus to best preserve its individual life. While only the barest outline of these adjustments to the water requirements of plants has been given here, the details form an almost dramatic picture of struggle of the different kinds of plants for survival. The extremes are the desert plants on the one hand and those of the rain forests in the tropics on the other. The chapter on Plant Distribution will show how important these water requirements of plants have been in determining what grows on the earth to-day.