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.
The habitat of this plant is streams and ponds. The plant is of aquatic habit. The stem does not rise out of the water. The submerged leaves are thrice forked, with long segments, tassellike, spreading. The floating leaves are nearly round, deeply cut into 3-5 wedge-shaped segments, stalked or stalkless. The flowers are white with yellow centres, the petals 7-9-veined, distinct, not falling, inversely ovate to wedge-shaped, longer than the sepals. The receptacle is conical. The flower-stalks are not longer than the leaves. The stigma is not as long as the stamens (which are numerous), and oblong, short, and blunt. The style is hooked. The achenes are smooth or hairy. The plant is floating or submerged. It is in flower between May and July, and is a herbaceous perennial.
Ranunculus lutarius, Boul. = R. intermedtus, Bab. - The habitat of this plant is damp ground and wet ditches. The plant has a suberect habit, with aerial stems. The leaves are 3 parts rounded, the lateral lobes with 3, the middle with 2-4, scalloped teeth. The divided leaves are few, rigid, not collapsing, and either floating or aerial. The submerged leaves with flat segments are seldom produced. The floating leaves are somewhat shield-shaped, deeply divided into 3 nearly to the base, the lobes wedge-shaped, inversely egg-shaped, 2-4 fid. The upper stipule is free. The flowers are pinkish - white, the petals little longer than the calyx. The petals may be longer and 5-veined. There are 5-10 stamens. The style soon falls, and is terminal, with a slender base, awl-like. The carpels are unequally inversely egg-shaped, much inflated, with a nearly terminal point. The inner edge is much rounded. The plant is in flower between May and July, and is a herbaceous annual.
The habitat of this plant is shallow-ponds, muddy places. The habit is prostrate. The stem may float (rarely) or creep on the mud. The leaves are opposite as a rule, rounded, heart-shaped, or ivy-like (hence hederaceus), with 3-5 shallow, entire, triangular, rounded lobes, widened at the base, and are usually spotted. The flowers are white, the sepals and petals of about the same length. The petals are 3-veined, distant, and narrow. The receptacle is smooth. The stamens are 6-8, as long as the pistil. The achenes are small, few, and blunt. The plant is prostrate. The flowers bloom between May and August. The plant is a herbaceous perennial.
The habitat of this species is ditches, muddy places, and ponds. The habit is erect. The stems are robust, succulent, hollow. The root is fibrous. There are submerged leaves which are different to the aerial leaves. The radical leaves are stalked, divided into three, with blunt, scalloped lobes, shining, smooth, the upper ones slightly hairy, and linear. The flowers are small, pale-yellow. The calyx is turned back, the sepals hairy. The honey-glands are round, open, bordered all round, not above. The achenes are smooth, oblong, numerous, wrinkled, furrowed one side. There is a very small style. The plant is 8-24 in. in height, and flowers between May and September. It is a herbaceous perennial.
The habitat of this plant is Highland lakesides. The plant is closely allied to the Lesser Spearwort, resembling it in habit. The stem is smooth, solitary, suberect, zigzag. The stem does not root at the nodes. The young radical leaves are numerous, small, and do not persist, being without any lamina. The later radical and lower stem-leaves are larger, with or without blunt, oblong to lance-shaped laminae. The upper stem-leaves are linear, lance-shaped, blunt, stalkless, or nearly so. The flowers are yellow, the petals inversely ovate, blunt. The carpels are inversely ovate, and pitted. The plant is 4-12 in. in height, flowering from June to August, and is a herbaceous perennial.
Ranunculus reptans, L - The habitat of this plant is sandy shores of Loch Leven, etc. The plant is prostrate in habit. It is very slender, and the stem roots at every arching internode. The leaves are linear, entire. The flowers are very small. The achenes are very small. The style is sub-cylindrical, and bent back. The carpels are bluntly beaked. The plant is 1-4 in. in height, and flowers between June and August. It is a herbaceous perennial.