Whilst we have been seeing all these peculiar things in the seeds which we have dug up, the plantlets which we have not disturbed have been coming through the soil. If we were to see the plant in [Fig. 195], as it was "coming up," it would look like [Fig. 196]. It is tugging away in getting its head out of the bonnet which is pegged down underneath the soil, and it has "got its back up" in the operation. In [Fig. 197] it has escaped from its trap and it is laughing and growing in delight. It must now straighten itself up, as it is doing in [Fig. 197], and it is soon standing proud and straight, as in [Fig. 189]. We now see that the reason why the "seed" came up on the plant in [Fig. 190], is that in some way the peg did not hold the seed-coats down (see [Fig. 195]), and the expanding leaves, being pinched together must get themselves loose as best they can.
There is another thing about this interesting squash plant which we must not fail to notice, and this is the fact that these first two leaves of the plantlet came out of the seed and did not grow out of the plant itself. We must notice, too, that these leaves are much smaller when they are first drawn out of the seed-coat than they are when the plantlet has straightened itself up. That is, these leaves increase very much in size after they reach the light and air. The roots of the plantlet are now established in the soil and are taking in food which enables the plant to grow. The next leaves which appear will be very different from these first or seed leaves.
These later ones are called the true leaves. They grow right out of the little plant itself. [Fig. 199] shows these true leaves as they appear on a young Crookneck squash plant, and the plant now begins to look much like a squash vine.
Fig. 197. The plant liberated from the seed-coats.
Fig. 198. The plant straightening up.
We are now curious to know how the stem grows when it backs out of the seeds and pulls the little seed-leaves with it, and how the root grows downwards into the soil. Now let us pull up another seed when it has sent a single root about two inches deep into the earth. We will wash it very carefully and lay it upon a piece of paper. Then we will lay a ruler alongside of it, and make an ink mark one-quarter of an inch from the tip, and two or three other marks at equal distances above ([Fig. 200]).[39] We will now carefully replant the seed. Two days later we will dig it up, when we shall most likely find a condition somewhat like that in [Fig. 201]. It will be seen that the marks E, C, B, are practically the same distance apart as before and they are also the same distance from the peg AA. The point of the root is no longer at DD, however, but has moved on to F. The root, therefore, has grown almost wholly in the end part.
