“They are all cruciferæ?”
“Yes, all cruciferæ. But their likeness is not confined to the shape of the blossom; their inner properties also, such as smell, taste, and the rest, are the same, or very nearly so. Consequently, the cabbage-weevil, as knowing a little creature as can be found, goes to the turnip when there are no cabbages to be had, to the colza if turnips also are lacking, or to other plants still, but always to some member of the cruciferæ family. Other insects show this same peculiarity, each species having its particular group of plants and going from one to another without ever making a mistake as to family.”
“Then they are expert botanists, I should say,” Jules remarked.
“One might almost think so; at least they show in their choice so keen a discernment that often men of science go to school to them to learn the various degrees of relationship in the plant world.”
“Oh, Uncle Paul, you are joking!” exclaimed Jules.
“Joking? Listen. You know the nasturtium, that beautiful orange-colored flower ending at the bottom in a kind of horn; and you know the mignonette, that sweet-smelling plant that Mother Ambroisine grows in the window.” [[337]]
“Yes, I know them.”
“Then tell me whether you find between mignonette, nasturtium, and cabbage any resemblance, any sign of plant-relationship.”
“No, indeed! Those three plants are wholly unlike one another: their flowers haven’t the same shape, nor their leaves, nor yet their fruit.”
“Well, my dear boy, you, who rather pride yourself on knowing something about flowers, really know much less about them than a poor little green caterpillar very common in our gardens; and many persons of far more learning than you could take lessons from this same caterpillar. It feeds indifferently on various cruciferæ, such as the cabbage, rape, and the turnip; but it also feeds on the nasturtium and the mignonette. Why? You must ask the scientists who make a thorough study of plants and are determined to find out the minutest details concerning them. They would tell you that there is something in their innermost structure, something invisible to our untrained eyes, that makes the nasturtium and the mignonette very nearly akin to the cruciferæ without looking like them. It is enough to puzzle anybody, I admit. A worthless caterpillar has, from the beginning of the world, eaten mignonette as well as turnip, cabbage as well as nasturtium, and has been familiar with plant-relationships unsuspected by science until our own time.”