Under such conditions it is not surprising that desert plants are among the most curious and weird members of the plant world. Every device both to retard transpiration and to store up water to last over a completely rainless period, may be found. In America, to which all the hundreds of different species of cactus are practically confined, we find giant forms, often covered with spines and prickles which prevent their destruction by cattle, and many others that hug the dry sandy soil with curious tortuous branches. None of them have leaves such as plants of the forest or grassland possess, for desert plants cannot afford the luxury of foliage that, because of too rapid water loss, would destroy their chance to survive. Cacti do produce tiny leaves at the ends of their joints, but as if recognizing the inhospitable world into which they are born, practically all of them drop off, so that for the great bulk of the life of most cacti only the bare branches are evident. In most kinds these branches are green, assume the functions of leaves, such as transpiration and the manufacture of food by photosynthesis. While in cacti and in the giant cactuslike spurges of South Africa the ability to store water is tremendously developed--our giant cereus or saguaro often holding 125 gallons--most desert plants rely upon retarding transpiration for their existence. Leafless shrubs and trees whose often spiny branches are green and perform, on a much-reduced scale, the function of leaves, are among the most common characteristics of desert plants. Some, as _Parkinsonia microphylla_ or paloverde, have tiny leaves which they put out during the spring showers, but quickly lose them as it gets hotter and drier toward midsummer. Many of the plants that do produce leaves regularly have the surface of them so shiny as to appear varnished, or so thickly coated with hairs as to simulate cotton or wool, both of which reduce transpiration. There are many plants, some of which do not even live in a desert but in a locally dry habitat, that also have the utmost development of structure to prevent transpiration. One of the most extraordinary is the vegetable sheep in New Zealand. An inhabitant of dry rocky places, its water supply, although rainfall is fairly abundant, is precarious due to drainage and the failure of the rock to prevent run-off. The different species of _Raoulia_, of which _R. eximia_ is one of the best known, are admirably adapted to exist under such conditions. L. Cockayne, an authority on the flora of that island, writes of these strange plants: “Perhaps the most striking denizens of rocks are the various kinds of vegetable sheep (species of _Raoulia_), which form hard cushions, mostly white, but occasionally green--and of enormous size. The raoulia cushions are all constructed on the same plan. Above, the stems branch again and again, and toward their extremities are covered with small woolly leaves, packed as tightly as possible.