CONVOLVULUS.
"What is this pretty pink flower," asked May, "with long trailing stems and leaves broadly arrow-shaped? From its resemblance to that beautiful convolvulus in the garden I should think it must be a smaller kind of that plant." You are quite right, it is a convolvulus, and its English name of Field Bindweed is expressive of the clinging habits of this plant; see how tightly it has wrapped itself round this tall blade of grass. Although a very pretty plant; with its pink flowers and darker plaits, its arrow-shaped leaves, and its fragrant smell, it is a troublesome weed to the farmer. Then there is the greater bindweed, with its large bell-blossoms sometimes white as snow, sometimes striped with pink, sometimes almost rose-colour, so often seen growing profusely over the tallest bushes. Both kinds of bindweed, however, are mischievous weeds; the large kind you may find in flower as late as September. Some of the bindweed family, I ought to say, are valuable in medicine. There is for instance the Convolvulus jalapa and Convolvulus scammonia, both of which are extensively used in medicine; the former a South American plant and the latter a Syrian one. Then there is the so-called sweet-potato, which is the root of Convolvulus batatas used in China, Japan, and other tropical countries as a wholesome food. Strange it seems that plants so closely related should differ so much in their properties.
The accompanying vignette may be supposed to represent Master Willy watching the movements of a snail.
WALK VIII.
JULY.
LET us have another stroll on the moors. We pass over a small brook on our way, and of course stop on the bridge and gaze into the little rivulet. What do I see about four yards off in the shade? A number of small dark-coloured patches which I recognise at once as one of our most beautiful fresh-water algæ. We will gather some from the bottom. There! the little tufts are attached to the upper sides of stones. When taken out of the water, the plant looks and feels like a mass of very dark jelly. I will float a piece out in this bottle of water. Did you ever see anything more beautiful? It consists of a number of delicate branches, each arranged in a bead-like row, and from a certain resemblance which these beaded rows bear to frog-spawn, as well as from their jelly-like consistency, this alga has received the name of Batrachospermum, which means "frogs' spawn." If we take a bit home and spread it out carefully on a piece of drying paper, separating the numerous beaded branches one from the other with the point of a needle, and leave it to dry gradually, we shall get a very pretty object indeed. As you may suppose, the plant is a most charming object for the microscope. "Do you think," asked Willy, "it would do in my aquarium?" I have several times tried it in an aquarium; it would live for a few days, then gradually lose colour and break to pieces. The fact is that, as Dr. Hassall says, these plants "inhabit mostly pure and running waters, being usually met with in fountains, wells, and streams, the force of which is not considerable." The frog-spawn alga, therefore, will not thrive in any but the purest water, and a gentle flow is necessary to its growth and health. "These plants are so exceedingly flexible," Dr. Hassall continues, "that they obey the slightest motion of the fluid which surrounds them, and would seem almost to be endowed with vitality; nothing can surpass the ease and grace of their movements. When removed from the water they lose all form, and appear like pieces of jelly without trace of organization. On immersion, however, the branches again quickly resume their former disposition. They adhere strongly to paper, and in drying frequently change to some other tint usually much deeper; on being moistened after long intervals they recover much of their original freshness; and it is even asserted that, after having lain in the herbarium for some years, when they are replaced in water in a suitable locality, they will vegetate as before." This last assertion I must say I do not credit. I shall never forget the delight I felt when I first made the acquaintance of this curious and graceful alga. From the eyes of how many people are its charms hidden! It is only those that look closely that would notice the little jelly-like tufts growing modestly in shaded places for the most part. This species, however, is common enough in gently flowing and shallow streams, and we may often come across it in our rambles if we take the trouble to use our eyes. There are other extremely beautiful forms of fresh-water algæ.