Papaver - Poppy. The Alpine Poppy (P.alpinum) is worthy of a place in the rock garden. The common form has yellow flowers, with white centers. Seed.

Petrocallis - Rock Beauty. On small sunny ledges in good soil this is a gem. P.pyrenaica bears a pro­fusion of sweetly scented, lilac flowers on dense tufts of foliage. Seed.

Phlox - Of these the Moss Pink (P.subulata), errone­ously known as P.setacea, is a dainty little evergreen with rosy flowers, rambling freely over stones and garlanding ledges. P.setacea is equally delightful, with soft pink flowers, it may be massed with its sub-variety P.s.violacea, whose deeper crimson flowers afford a pretty combination.

Polygonum - Knotweed. The Himalayan variety P.affine is a good plant for moist places, its spikes of rosy red flowers producing a delightful effect. The foliage is brilliantly colored in autumn. P.vaccinifolium is best in rough, rocky places where it can ramble at will among stones and boulders.

Potentilla - Cinquefoil. Plants of easy culture, thriving in exposed places in loamy soil. The best of the dwarf Alpines are P.nitida (Shiny Cinquefoil), with silvery leaves and rosy flowers: P.alpestris (Alpine Cinquefoil), much larger, with bright yellow blossoms, and P.alba (White Cinquefoil), a dwarf, variety, bearing white and orange flowers.

Primula - Primrose. One of the largest and best of all the rock plant families. For rock gardens the follow­ing should be grown: P.denticulata, P. farinose, P.rosea, and P.sieboldi.

Pyrola - Winter-green. Beautiful plants for half shade. P.rotundifolia, with tall stems and drooping racemes of numerous white flowers, should be grown together with its sub-variety P.r.arenaria. The flowers are sweetly scented. Light sandy soil.

Ranunculus - Crowfoot Buttercup. Of simple culture, the Buttercups thrive in any fairly moist sandy soil. R.alpestris, with deep glossy foliage, and large pure white flowers and clustered yellow stamens, is one of the best. R.glacialis, in the coolest positions, and R.amplexicaulis (White Buttercup) are good for rock gardens.

Sanguinaria - Bloodroot. A very desirable plant. S.canadensis forms dense clusters of large glaucous leaves, on which numerous white flowers with yellow stamens rest like miniature Water Lilies. Division.

Saponaria - Soapwort. The rosy flowered S.ocymoides is a beautiful plant for mantling the edges of rocks. Poor, dry soil.

Saxifraga - Rockfoil. Perhaps the best known of all rock plants. S.cotyledon (Pyramidal saxifrage), S.longifolia, S.oppositifolia, S.umbrosa (London Pride).

Sedum - Stonecrop. Hardy dwarf plants for rock crevices and the higher ledges. S.acre (Wall Pepper) grows freely on walling, and is bright by reason of its vivid yellow flowers. S.stoloniferum (Purple Stone­crop), with large leaves, and S.sieboldi, useful for draping the edges of stones, are among the best.

Sempervivum - Houseleek. Dwarf succulents, thriving in the poorest soil. The Cobweb Houseleek (S.arach­noideum) is very quaint, with its myriad silver leaf rosettes covering the ground like a web. S.triste, with red leaves, is distinct. Offsets.

Silene - Catchfly. Invaluable for rock gardens. The Alpine Catchfly (S.alpestris) is a hardy white flowered kind. S.virginica (Fire Pink), though impatient of too much moisture, is very beautiful. It has vivid scarlet flowers. Seed.

Soldanella - In a moist, deep soil between the higher rocks, Soldanellas are delightful. S.alpine has bell­shaped flowers of a pale blue color, the carpet of feathery foliage in this variety giving an added charm. They must not be grown near large plants. Division.

Thymus - Thyme. On the outskirts of the rock garden where there are no small plants, masses of creeping Thyme are very beautiful. The poorest and driest soil will suffice. Two beautiful kinds are the wild white Thyme (T.serpyllum albus) and the woolly­-leaved Mountain Thyme (T.lanuginosus), with purple flowers. Full exposure to sun.

Tiarella - Foam Flower. An exquisite plant of the hardiest description. The trailing foliage is tinged with red and bronze, and the graceful spikes of creamy pink flowers, when massed, give the rocks and stones an almost foam flecked appearance. Frequent division.

Veronica - Speedwell. The trailing kinds should be found in all rock gardens. V.rupestris and V.prostrata are good. V.spicata, a native plant, soon covers the ground with neat patches of foliage. Sandy loam.