This section is from the book "British Wild Flowers In The Four Seasons", by Thomas Moore. Also available from Amazon: British Wild Flowers.
* Leafstalks without real leaflets. † Flowers red.
L. Nissolia: annual; stems erect, glabrous, branching from the base, about one foot high; leaves reduced to linear, grass-like, flattened leafstalks ending in a fine point, without leaflets or stipules; peduncles long, bearing one rarely two small pale red flowers; pod long, narrow, and straight. - Grass Vetch. - Bushy places and stony pastures. Fl. June.
†† Flowers yellow.
L. Aphaca: annual; stems weak, branching, glabrous, about one foot long; leaves reduced to slender branched tendrils between the pairs of large broadly heart-shaped or sagittate stipules, which appear like simple opposite leaves; peduncles long and slender, with one or rarely two small yellow flowers; pod flattened, glabrous. - Cultivated places, occasionally. Fl. June to August.
** Leaves with one pair of leaflets. † Flowers yellow.
L. pratensis: stems much branched, glabrous, straggling or half climbing to the length of 1-2 feet; stipules large, broadly-lanceolate, sagittate; leaflets narrow-lanceolate or linear; peduncles elongated, with a short raceme of about 6-10 yellow flowers; pod glabrous. - Moist meadows and pastures. Fl. July, August.
†† Flowers red.
L. sylvestris: stems glabrous, straggling or climbing, 3-6 feet high, the angles expanded into narrow green wings; leafstalks flattened or winged; leaflets long-lanceolate; stipules narrow; flowers in loose racemes, large, pale reddish-purple, the standard broad, with a green spot on the back. - Hedges thickets, and bushy places. Fl. July to September.
The Everlasting Pea of our gardens is a broad-leaved variety, with larger and more richly-coloured flowers.
*** Leaves with 2-4 pairs of leaflets.
L. macrorrhiza: tuberous; stems glabrous, erect, simple or nearly so, 1/2-1 foot high; leaves without tendrils; leaflets usually 2 sometimes 3-4 pairs, oblong-lanceolate or linear; peduncles slender, bearing a loose raceme of 2-4 bright reddish-purple flowers; pod glabrous. - Thickets and open woods. Fl. June, July.
 
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