This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
This plant is found in cornfields, cultivated fields, and waste places. The habit is erect. The stem is short, branched, with short hairs, dense, and turned back. The leaves are narrowed below, stalked, egg-shaped, oblong, lance-shaped, toothed, the upper similar and large. The flowers are lilac, in axillary, distant whorls, none at the top, the calyx bell-shaped, with triangular, short teeth, as broad as long. The throat of the calyx is naked. The corolla is lined with hairs and hairy outside. The bracteoles are acute, and not as long as the flowers. The nutlets are dry and smooth. The plant is 1-2 ft. in height, and flowers late, like the rest of the group, from August to October, and is a herbaceous perennial.
The habitat of this plant is cornfields, fields, and waste places. The habit is prostrate, or may be ascending. The stem is weak, hairy at intervals, branched from the base, rooting below. The radical leaves are shortly stalked, the upper leaves stalkless, egg-shaped, heart-shaped, blunt, scalloped. The flowers are purple, in whorls of 4-6. The bracts are stalkless, acute. The flower -stalks are short. The small corolla is slightly longer than or equal to the calyx. The nutlets are covered with dots and warted. The plant is 6-18 in. in height, and flowers from April to November, being a herbaceous annual.
This plant is found in cornfields, cultivated ground, and waste places. The habit is erect. The stem is softly downy, with hairs bent down, not thickened at the joints. Briquet says that the thickened nodes are differentiated to cause movements, such as geotropism and heliotropism, these swollen nodes being marked in Galeopsis Tetrahit (Vol. III). The leaves are egg-shaped, lance-shaped, toothed. The flowers are purple, the lower lip mottled, with the tube of the corolla equal to the calyx, in separate whorls. The nutlets are flattened, rounded. The plant is 10-12 in. in height, and flowers from July to October, being a herbaceous annual.
This plant grows in sandy and gravelly districts. It is distinguished from G. Ladanum by the narrower leaves united below, toothed at intervals, or nearly entire, the upper whorls close, the tube exceeding the corolla and the slightly notched upper lip of the corolla. It flowers in August and September, and is an annual.
The habitat of this plant is sandy cornfields and cultivated ground. The habit is similar to that of G. Ladantun. The stem is not thickened at the nodes, downy, glandular, with hairs turned back. The leaves are broad, egg-shaped, lance-shaped, toothed, downy both sides, soft. The flowers are pale-yellow, white or purple, the upper corolla lip deeply notched, the calyx glandular, downy, the teeth not longer than the tube. The whorls are dense. The bracteoles are small. The plant is from 10-12 in. in height. July and August are the months in which it is in flower. It is a herbaceous annual.
The habitat of this plant is cultivated ground. The habit is as in the Common Hemp Nettle. The stem is thickened at the nodes, with stiff hairs. The leaves are oblong, egg-shaped, with a long point, toothed. The flowers are large, yellow, and with a purple spot on the lower lip, the corolla large and broad, the tube longer than the bell-shaped calyx, the upper lip arched, as broad as long. The teeth of the calyx are not so long as the tube. The nutlets are convex above and dark-brown, the inner angle rounded downwards. The plant is 1-2 ft. in height, and is in flower in July and August, being a herbaceous annual.