Why Are Leaves Not All the Same Shape?
Leaves are of different shapes because they belong to different families of plants or trees. They are a good deal like people in this respect. Hardly two people in the world look exactly alike, but there is a distinct family resemblance in members of the same family. It is difficult to say just what happens inside the tree to determine the shape of the leaf and that causes them to possess different shapes from others. The shape of the leaf is a mark of identification of the family to which the tree or plant belongs, just as you can tell from a dog’s ears and from other characteristics what his breeding has been. In the case of plants and trees however it is quite probable that the shape and texture of the leaves has been developed as the result of the conditions under which the plant grows. A plant or tree throws off oxygen and takes in carbonic acid gas through the surface of the leaves. To thrive and be healthy it must secure just the proper amount of this food and as the quantity of food taken in depends upon the amount of surface exposed through the leaves, each particular tree or plant has developed in its own direction in this respect until this feature of their structures has been adjusted properly to their needs. It is a good deal like the radiation of heat in your home.