These leaves grow in pairs, on alternate sides of the stem: they are oval, and slightly hairy, and the edges are cut all round into sharp teeth. Where each leaf joins the stem a flower-stalk rises, and in the Dog's Mercury there are two kinds of flowers. On one stalk you find groups of small flowers clustered at close intervals round the stalk. Each of these flowers has three broadly pointed green sepals, which curl slightly at the tips. In the centre of these sepals rises a large bunch of eight to sixteen yellow-headed stamens. In these flowers there are no petals, and no seed-vessel. But you will find different flowers on another plant. These flowers have also three green sepals, and are without petals. But in the centre lie two hairy green seed-vessels, like small peas joined together, and on the top of these seed-vessels are two tiny green horns. 3. COMMON NETTLE What child does not know the Common Stinging Nettle? We have all learned to avoid it after having felt its sting. You find this Nettle everywhere in late summer and autumn. It has a four-sided stem, which is rough with bristly hairs. The leaves grow opposite each other in pairs with a good space between each pair. They are dark green and rather coarse, and are covered with a network of veins and with many stinging hairs. Close to the stalk the leaves are heart-shaped, but the tips are sharply pointed and the edges are deeply toothed all round. The flowers of the Common Nettle grow on slender stalks which rise between the leaf and the main stem. These flowers are green, and they are very small and unattractive. On one flower you find four green sepals and four yellow-headed stamens, but there are no petals and no seed-vessel. In another flower there is a fat green seed-vessel, with four sepals round it. PLATE XXXI: 1. PURPLE SEA ROCKET 2. CUCKOO FLOWER OR LADY'S SMOCK 3. MARSH CINQUEFOIL 4. WATER AVENS 1. PURPLE SEA-ROCKET The Purple Sea-Rocket grows abundantly all summer on most of our seashores. It is a bushy plant with many branches, and you will recognise it by its thick and fleshy green leaves. The flowers are a pale lilac colour, like those of the Cuckoo Flower. Some of them grow on heads at the end of the main stem, and others have short stalks which branch from each side of this stem. In this plant there are always buds in a cluster at the end of the stem, and those flowers that come out first grow further down the stem. Behind the lilac flowers there are four small brownish-green sepals. When these fall off, after the flower is withered, the seed-vessel which lies inside grows into a small green pod. The pod is in two pieces and looks as if it were joined in the middle. You will see a great many of these tiny pods growing on each side of the main stalk where there have been flowers. The stem of the Sea-Rocket is very smooth and juicy. The leaves are long and feather-shaped, and they are cut very irregularly into fingers all the way round.