BUTTERWORT  , the popular name of a small insectivorous plant, Pinguicsda vulgaris, which grows in wet, boggy

land . It is a herb with a rosette of fleshy, oblong leaves, 1 to 3 in. long, appressed to the ground, of a pale colour and with a sticky surface . Small insects settle on the leaves and are caught in the viscid excretion . This, like the excretion of the sundew and other insectivorous plants, contains a digestive ferment (or enzyme) which renders the nitrogenous substances of the body of the insect soluble, and capable of absorption by the leaf . In A, leaf of Butterwort (Pinguicula vulgaris) with left margin inflected over a row of small flies . (After Darwin.) B, glands from surface of leaf by which the sticky liquid is secreted and by means of which the products of digestion are absorbed . this way the plant obtains nitrogenous food by means of its leaves . The leaves bear two sets of glands, the larger borne on usually unicellular pedicels, the smaller almost sessile (fig . B) . When a fly is captured, the viscid excretion becomes strongly acid and the naturally incurved margins of the leaf curve still further inwards, rendering contact between the insect and the leaf-surface more complete . The plant is widely distributed iu the north temperate zone, extending into the arctic zone .