1. Habit of growth.—Carefully dig up a plant of the common horsetail. Notice (a) the deep, creeping, underground stems; (b) the thin wiry roots springing from the stem; (c) the two kinds of upright shoots or haulms: one kind (Fig. 152)—to be found in summer—being thin, and giving rise to tiers of green branches, which come off like the ribs of an umbrella; the other kind (Fig. 153), coming up in March, being paler in colour, without branches, and bearing little cones at the apex. 2. The underground stem.—Make out that the stem is distinctly divided into nodes—marked by toothed leaf-sheaths—and internodes. Does it branch? Notice that some of the branches are swollen, forming tubers. 3. The roots.—These are thin and wiry, and come off from the stem. Do they come off at the nodes or at the internodes? 4. The branched haulms.—Observe that each is divided into [Pg 192] nodes—marked by toothed leaf-sheaths—and internodes. Are the internodes smooth or ridged? From what parts of the haulms do the lateral branches arise? Carefully tear down a leaf-sheath to see its relation to the branches. Notice that the branches themselves branch repeatedly. What is the colour of the branches? 5. The cone-bearing haulms.—Do these haulms appear earlier or later than the others? What is their colour? Does a cone-bearing haulm give rise to branches at the nodes? Examine the cone with a lens and see that it is covered with hexagonal scales. Does the hexagonal shape allow the scales to be more closely packed? Take off a scale with a needle and notice, with the help of a lens, the spore-boxes attached to its inner surface. Fig. 152.—Sterile Haulms of Horsetail. Fig. 153.—Fertile Haulms of Horsetail. 6. The prothallus.—Dry a ripe cone and shake it over paper to collect the spores. Sow these on moist soil, and try to raise prothalli. [Pg 193] The general appearance of the horsetail.—The common horsetail (Fig. 154), which may be found in hedgerows and cornfields, is not in any respect showy. It rarely exceeds a few feet in height, and does not attract attention by any display of bright colours. The plant has stiff, jointed stems or haulms, standing gracefully erect and bearing rings of small united leaves at intervals. The branches arise just above the leaves, and alternate with them: several coming off at each level, somewhat like the ribs of an umbrella. The whole plant has thus a rather stiff and formal aspect. Fig. 154.—Common Horsetail. (× ⅙.) 1, Fertile haulms, terminating in cones (a): 2, a sterile haulm; a, tubers: 3, scale of cone with spore-boxes (mag.): 4, scale with ruptured spore-boxes (mag.): 5, 6, 7, spores (mag.).