Among these seeds, that of the wild-oat is chief. When the air is moist, the long bristles, called awns, on the seed, squirm and twist. In old times, before people knew why this was, they said that this seed was a witch! There is a marigold which grows at the Cape of Good Hope, and in dry weather has its head of seeds held close, like a round button. When rain is coming, this seed-head opens out, like a star with many points. Do you see the use of these motions? The wild-oat, as it wriggles and twists back and forth, from the dampness of the air, or earth, twists its way into the soil. It plants itself by these motions. The marigold keeps its seeds safe in dry weather, which would kill them. When rain comes, it opens the seed-head. Then the seeds fall out on moist earth, where they will sprout and grow. Some seed-pods fly open when they are dry. The sand-box tree has seed-pods as large as an orange. They fly open in dry weather. What is the reason of all these queer actions of the flowers? No doubt they are all due to light and moisture. To light, most of all. The little pimpernel probably needs much heat and light to open its petals. Even a little moisture in the air, or a little less light than it likes, will cause it to keep shut. A pimpernel in full bloom will close its blossoms almost as soon as you pick it. Very likely the slight moisture of your hand causes it to do that. This motion of closing, during rain, may be very useful to some flowers. A frail flower with a large cup, such as a tulip or crocus, might, if open, be broken to pieces by a heavy shower. These flowers fold up, and expose only a close-pointed bud, to the storm. Then no rain can get among the petals. Also, the rain might break the large pollen cases of the tulip, and wash the pollen all away. So, if the convolvulus had its long tube filled with water, the stamens and pistil would perhaps be harmed, and its seeds would not be able to grow. LESSON XIV. PLANT CLOCKS. I knew an old man who made a great clock for his grandchildren. What kind of a clock do you suppose it was? The clock was in the garden, and it was made of flowers. Did it tell the time well? Only pretty well. Flower clocks are as liable to get out of order as clocks made at a factory. This clock was a great flower bed, divided into twelve parts. The divisions were marked out by little rows of box-plants. In the middle was a post three feet high. It had two clock hands on it, but _they_ were only for show. They did not move. But the post had a sun-dial on it, and that gave true time. So the children could tell when the flower clock was not working well. As there are twelve hours of day and twelve of night, and some plants open only at night, each of the twelve divisions of the clock was divided into two parts by a little line of red colors. On one side of this were the night bloomers, on the other side the day bloomers.