"Several kinds of trees of various sizes and forms were examined along this power transmission line, and all were found to be singing with a loud voice the fundamental note characteristic of the line current. Indeed, the strip of vegetation along this line has thus been singing continuously, day and night, for several years, since the operation of the line began; it needed only the electro-magnetic ear to make the sound apparent....
"The general appearance of vegetation along this route is certainly vigorous."[101]
An interesting little experiment was carried out by the author in Glasgow, with the kind help of Professor Blyth, at the Glasgow and West of Scotland Technical College. By attaching one wire to the upper part of the stem of a young pot-plant whilst the other wire was inserted in the base of the stem, it was easy to show that an electric current was passing—at any rate, during the daytime. In the evening, however, this was not at all distinct. That such currents do occur in living trees seems to be admitted. A similar current was not found in a stick of dead-wood. The mere passage of the water through the plant in transpiration might, however, cause such a current, for the water is evaporated at the leaves.
A strong electric shock may of course electrocute a plant by killing the cells. It is possible to cause the Mimosa leaves to close by means of an electric shock.
CHAPTER XVI
ON FLOWERS OF THE WATER
The first plant—Seaweeds in hot baths—Breaking of the meres—Gory Dew—Plants driven back to the water—Marsh plants—Fleur-de-lis—Reeds and rushes—Floating islands—Water-lilies—Victoria regia—Plants 180 feet deep—Life in a pond, as seen by an inhabitant—Fish-farming—The useful Diatom—Willows and Alders—Polluted streams—The Hornwort—The Florida Hyacinth—Reeds and Grass-reeds—The richest lands in the world—Papyrus of Egypt—Birds and hippopotami—Fever and ague.
WHAT was the first green plant? When was the surface of the earth first covered with flowers? Such questions are quite impossible to answer. We cannot even tell how plants ever came to exist on the earth at all. Wonderful as are the stories of the hardihood of bacteria, of spores, and of seeds, it is not possible to imagine that they could have been whirled or drifted through infinite space to this particular planet.
Yet it is at least probable that the first real plant on this world was a seaweed or alga.
In Germany and Austria there are certain springs in which the water coming from immense depths is at an exceedingly high temperature. These hot springs are used as natural hot baths, and have many interesting peculiarities. Amongst others there is the fact that certain seaweeds or algæ are found luxuriating in the hot water. Some of these can even live in springs with a temperature of 176° F.!