It is in order to catch the wind-borne pollen-grains that the stigmas of grasses are branched and feathery. A great waste of pollen is obviously entailed by this method. But on the other hand it must be remembered that insect-pollinated flowers have to pay for their privileges by storing nectar in cunningly hidden pockets, and by advertisement-expenses, all of which the grasses avoid.
Fig. 101.—Meadow Fescue.
A, spikelet with two open flowers (× 1½);
B, a flower from which the outer pale has
been removed (× 6).
The ovule is fertilised in the usual way, by a pollen tube growing down the style from a grain on the stigma. As a result of fertilisation the ovary becomes a fruit containing one seed which fills it. In many cases (e.g. barley and oats) the pales still remain in position and adhere to the fruit. When the awn is present it may play an important part in distributing the “seeds” by clinging to the hides of animals, etc. Sometimes the awn is of use in fixing the grain in position on the ground until the seed has germinated.
The structure of a grass seed has already ([p. 19]) been studied in the wheat and maize. The developing embryo ([p. 21]) lives upon a store of food called the endosperm ([Fig. 16]) until its roots and leaves are sufficiently advanced to make food for themselves.
29. SOME COMMON GRASSES.
1. The fescues.—Gather plants of meadow fescue, and examine the habit of growth (in tufts), the broad leaves, and the nodding panicles and the flowers. Also examine the “seeds.”
Compare sheep’s fescue ([Fig. 102]), and notice the very fine leaves. The outer pales are awned.
2. The meadow grasses.—Examine the various species of meadow grass ([Fig. 103]). They can be distinguished from each other by the characters of the ligules. Notice the tree-like habit of the panicles and compare them with the fescues. The meadow grasses never bear awns. Notice the woolly “webs” at the bases of the “seeds.”