Uncle Paul then led the children into the garden to fix in their minds by observation the lesson they had just learned. “Gather haphazard,” said he, “the first leaves you come to; then examine them and tell me how many cotyledons the seed must contain. First, here is the iris, with large blue flowers and sword-shaped leaves.” “I see,” said Jules, “veins running in regular lines side by side, without ever joining one another. Since these veins are parallel the iris seed has only one cotyledon.” “And this blade of grass, this also that I pick from a corn-stalk?” asked his uncle. “They, too, have parallel veins, both of them; and so their seeds must have only one cotyledon.” “And this grape-leaf, this leaf of the cherry tree?” “It’s my turn now,” Emile hastened to interpose. “The veins form a sort of lace with very fine meshes. The grape and the cherry have two cotyledons.” “It is as easy as that, my friends. The leaf with its arrangement of veins shows us the fundamental characteristics of the plant. It tells us whether the germ is fed by one nursing-leaf or two, whether the young plant comes up with one seminal leaf or two.” CHAPTER XXIX GERMINATION “The germ in the heart of the seed is in a state that may be likened to deep sleep: its life is, as it were, arrested, suspended. But under the stimulus of certain conditions it awakens, throws off its coverings, gathers strength from its stored-up food, unfolds its first leaves, and appears above ground. This opening of the seed is called germination. Moisture, warmth, and air are the determining causes; without their coöperation the seed would remain a certain length of time in good condition for sowing, after which it would wither and lose its germinating power. “No seed germinates without the help of moisture. Water plays a multiple part. First it soaks into the germ and the parts surrounding it, causing these to swell more than the envelope, so that the latter, however hard a shell it may be, is burst open. Through the cracks of this broken envelope the gemmule pushes out on one side and the radicle on the other, and henceforth the little plant enjoys the benefit of sun and air. Germination is more or less slow according to the degree of resistance offered by the walls of the seed. If these are hard and stony it is only with extreme slowness that the germ absorbs moisture and manages to burst its cell. Therefore, to shorten the period of germination care is taken to thin the shells of excessively hard seeds by rubbing them with a stone.