4. Human needs and the needs of plants. We must not forget that plants as well as animals are living things growing from infancy to old age, needing food and protection, and bearing offspring. Their various parts may be useful to us, but primarily are of use to the plants themselves. The plant-food which we take for our use, the plant had accumulated for its own purposes. The thorns which make a hedge effective against intruders, serve similarly as a defense to the shrub which bears them. Not only then as contributors to our welfare, but as sharers in the mysterious gift of life, should plants have a profound interest for mankind. How plants obtain their food, how they avoid injury, in what respects they are like animals, and how they differ from them- such questions soon press for an answer, and then it is seen that all plants, even the most humble, may have secrets of value to tell us.