Of a like nature are fruits of thistles, fireweed, prickly lettuce, sow thistles, scabiosa, valerian, cat-tail flag, cotton grass, some anemones, smoke tree, virgin's bower, and some of the grasses.
27. How the lily sows its seeds.—Ripened pods of lilies usually stand straight up on a stiff, elastic stem; beginning at the top, each one slowly splits into three parts, which gradually separate from each other. Why do they not burst open all of a sudden, like pea pods, and shoot the seeds all about and have the job done with? Or why does not the pod burst open at the lower end first, instead of the upper?
| FIG. 33.—At the left a dry fruit of a lily opening to permit seeds to dry and the wind to enter; to the right, a fruit later in the season. Two views of a flat seed. |
Observe that the three opening cells are lashed together loosely with a latticework. No slight breeze can dislodge the seeds, but just see how they behave in a good gale! The elastic stems are swayed back and forth against each other, and some of the upper seeds are tossed out by the wind that passes through the lattice, and at such times are often carried to some distance. The seeds at the top having escaped, the dry pods split down farther and still farther and open still wider, till the bottom is reached. As the seeds are not all carried away the first or even the second time, and as succeeding breezes may come from different directions, it is thus possible for the lily to scatter its seeds in all directions.
The seeds of the lily are flat, very thin, and rather light, not designed to be shot out like bullets, but to be carried a little way by the wind; the pods are erect, and open at the top, that the seeds need not escape when there is no wind or unless some animal gives the stem a strong shake. The latticework was made for a purpose, and the gradual opening of the pods prevents the supply from all going in one direction or in one day, for a better day may arrive. The student will look for and compare the following: Iris, figwort, wild yam, catalpa, trumpet-creeper, centauria, mulleins, foxglove, beardtongue, and many other fruits.
28. Large pods with small seeds to escape from small holes.—The large ripe pod of the poppy stands erect on a stiff stem, with a number of small openings near the top. The seeds are nearly spherical, and escape, a few at a time, when the stem is shaken by the wind or some animal, thus holding a reserve for a change of conditions. Here is an illustration of ripe pods of a bellflower, Campanula turbinata, nodding instead of erect.
| FIG. 34.—Ripe pod of poppy on an erect, stiff stem, ready for wind or animal to shake out a few seeds at the top. | FIG. 35.—Ripe pods of bellflower bent over; the holes opening when dry to allow seeds to be shaken out. |
The small holes are still uppermost, but to be uppermost in this case it is necessary for them to be at the base of the pod.