Now the sunflower we have just thought of is probably growing in a garden well looked after by a gardener, who sees that it gets all the light and water and just the kind of soil it needs. It is therefore protected and cared for to a certain extent, but who looks after the wild plants which manage to grow everywhere? These have not only their own lives to live, but by their own efforts must overcome difficulties which are not even felt by the cultivated ones. They succeed in a wonderful way, and some plants manage to grow under very difficult conditions, even in places where they get no water for months under a burning sun, or in forests where the overshadowing trees cut off the light and rain, or under the water where they get no direct air. They have to do all the usual work of plants, and at the same time struggle against the hardships of their surroundings. They are like men fighting for their lives with one hand and doing a piece of work with the other. The result of this is that they sometimes make themselves strange-looking objects, and in some plants which have had a very hard struggle it is difficult to know which part of the plant is which. Look, for example, at a Cactus (~see~ fig. 48), which grows in the desert; it appears to have neither stem nor leaves like an ordinary plant, and to consist merely of a roundish green mass covered with needle-like prickles. Yet when you come to study the Cactus you will find out that the thick, fleshy mass is really its stem, and the prickles its leaves which have taken on these strange shapes. By means of its unusual form the Cactus can live where our common plants would die of the dry heat in a day or two. The power plants have of changing their bodies so as to fit themselves to live under all kinds of conditions is one of the strongest proofs that they are alive. All the parts of plants have some special life-work, just as we have legs and arms for different purposes, and every part is formed in some way to suit the needs of the plant and help it to get on well in its home. The main thing to realise at the beginning of the study of plants is that they are living things, and therefore to try to discover the importance of the shape and arrangement of all their parts and their relation to the life of each plant as a whole. We will begin by looking carefully for all the signs of life in them, and noting how often these are the same as those of the animals, even though the whole plant-body is so different from that of an animal. CHAPTER II. SIGNS OF LIFE [Illustration: Fig. 1. Jar (A) with well-fitting cork, in which young bean plants are growing. The tube leading from the jar dips into dish of water (~s~) which has risen to levels marked in the course of three days. (~b~) Small tube of caustic potash.]