Page:Popular Science Monthly Volume 30.djvu/704

682 fold her leaflets. This same effect is also induced by cold and darkness.

The flowers of many plants are found in certain ways to be greatly dependent on temperature and on light. They open in the morning when the sun has reached a certain place in the heavens, and close again at a stated time at night.

Some plants can open their flowers or parts of them very quickly. For instance, the Martha of the tropics, on the approach of an insect, ejects its pollen suddenly, and then as quickly closes the entrance to the flower, and refuses the insect admission. Motion of a different nature is shown by the climbing plants that were so closely studied by Darwin.

At times one hears or reads of the wandering of plants. But how is it possible that firmly rooted plants should be capable of changing their position? And yet this is so. In most cases, it is true, the removals are made merely by the seeds and not by the plant as a whole. Sometimes, however, the whole plant starts out to travel; this is generally accomplished by the friendly aid of the wind. The world-famed Anastatica, the rose of Jericho, comes in for mention here. It has the peculiar property of spreading out its branches, that at other times are folded to a ball, whenever its roots are moistened by water. In its dreary home, the deserts surrounding the Red Sea, it is but slightly fastened in the loose sand. Without much trouble it is torn from its bed by the winds and borne to great distances.

Some species of algæ, which form green or yellowish-green masses on the surface of placid waters, are thrown on the land by inundations, and are kept back after the waters have subsided, and finally dry into a peculiar matted substance not unlike coarse packing-paper. This is taken up by a strong wind and carried away. These wandering masses, which some people have readily connected with superstitious conceptions, are called "meteor paper." The water-pest is another plant that spreads itself in the same manner; as far as can be ascertained, it was transplanted in 1835 from North America to Ireland, and from there to the European Continent.

The majority of plants, however, are spread by the aid of their seeds, which are covered with hair or a fine woolen fiber, and can thus be easily scattered about by the winds, just as some varieties of spiders, in spring and autumn time, clinging to a silken thread, intrust to the winds the choice of their future home.

Let us now turn to a group of plants which claim interest by being possessed of a faculty generally attributed to animals only. Not satisfied with the nourishment which the humidity of the soil and the atmosphere afford, they seek to obtain a kind of food which Nature has, strictly speaking, denied them. I mean the insect-eating plants.

The knowledge of the existence of these curious beings is not really of a recent date, but former investigations remained unheeded.