The LARGER or HYSSOP SKULLCAP (S. integrifolia) rarely has a dent in its rounded oblong leaves ,which, like the stem, are covered with fine down. Its lovely, bright blue flowers, an inch long, the lips of about equal length, are grouped opposite each other at the top of a stem that never lifts them higher than two feet; and so their beauty is often concealed in the tall grass of roadsides and meadows and the undergrowth of woods and thickets, where they bloom from May to August, from southern New England to the Gulf of Mexico, westward to Texas. This tribe of plants is almost exclusively North American, but the hardy MARSH SKULLCAP or HOODED WILLOW-HERB (S. galericulata), at least, roams over Europe, and Asia also, with the help of runners, as well as seeds that, sinking into the soft earth of swamps and the borders of brooks, find growth easy. The blue flowers which grow singly in the axils of the upper leaves are quite as long as those of the larger and the showy skullcaps; the oblong, lance-shaped leaves, which are mostly seated on the branching stem, opposite each other, have low teeth. Why do leaves vary as they do, especially in closely allied species? "The causes which have led to the different forms of leaves have been, so far as I know," says Sir John Lubbock, "explained in very few cases: those of the shapes and structure of seeds are tolerably obvious in some species, but in the majority they are still entirely unexplained; and, even as regards the blossoms themselves, in spite of the numerous and conscientious labors of so many eminent naturalists, there is as yet no single species thoroughly known to us." GROUND IVY or JOY; GILL-OVER-THE-GROUND; FIELD BALM; CREEPING CHARLIE (Glecoma hederacea; Nepeta Glechoma of Gray) Mint family Flowers - Light bluish purple, dotted with small specks of reddish violet; growing singly or in clusters along stem, seated in leaf axils; calyx hairy, with 5 sharp teeth; corolla tubular, over 1/2 in. long, 2-lipped, the upper lip 2-lobed, lower lip with 3 spreading lobes, middle one largest; 4 stamens in pairs under upper lip; the anther sacs spreading; pistil with 2-lobed style. Stem: Trailing, rooting at intervals, sometimes 18 in. long, leafy, the branches ascending. Leaves: From 1/2 to 1 1/2 in. across; smooth, rounded, kidney-shaped, scallop-edged. Preferred Habitat - Waste places, shady ground. Flowering Season - March-May. Distribution - Eastern half of Canada and the United States, from Georgia and Kansas northward.