Primroses.—­See “Primulas,” and “Streptocarpus.”

Primulas.—­This genus embraces the Auricula, the Polyanthus, and the Primrose.  The greenhouse varieties are among the most useful of our winter-flowering plants.  The seed may be sown at any time from March to July in a pot of two-year-old manure, leaf-mould, or fine, rich mould, but not covering it with the soil.  Tie a sheet of paper over the pot and plunge it in a hotbed.  Sufficient moisture will be communicated to the seed by keeping the paper damp.  When the plants make their appearance remove the paper and place the pot in the shady part of the greenhouse.  When they are strong enough to handle, pot off into 4-1/2 in. pots, and stand them near the glass.  The roots may be divided as soon as the plants have done flowering.  The hardy kinds may be sown in the open.  It should be borne in mind that the seed must be new, as it soon loses its germinating properties.  These flower in March or April.  Height, 6 in.

Prince’s Feather.—­An ornamental hardy annual, producing tall spikes of dark crimson flowers and purple-tinted foliage.  It is not particular as to soil, and merely requires sowing in the open in spring to produce flowers in July.  Height, 2 ft.

Privet.—­See “Ligustrum.”

Prophet’s Flower.—­See “Arnebia.”

Prunella Grandiflora.—­A pretty hardy perennial, suitable for a front border or rock-work, bearing dense spikes of flowers from May to August.  It grows well in any ordinary soil, and is propagated by division.  Height, 6 in.

Pruning.—­The main objects to bear in mind in Pruning any kind of bush or tree are to prevent a congested growth of the branches, to remove any shoots that cross each other, as well as all useless and dead wood, and to obtain a well-balanced head.  It may be done either in August or in the winter when the sap is at rest, after the worst of the frosts are over, the end of February being usually suitable; but the former period is generally acknowledged to be the better, especially for fruit-trees.  The cuts should be clean and level, and when a saw is used should be made smooth with a chisel and covered with grafting wax.  In all cases as little wound as possible should be presented.  Root-pruning has for its object the suppression of over-vigorous growth and the restoration of old trees to a bearing condition.  It consists in taking off all the small fibres, shortening the long roots to within 6 or 8 in. of the stem, and cutting away any bruised or injured roots before the trees are first planted out.  The mode of procedure in the case of old or unproductive trees is to open the earth in autumn 3 ft. from the stem of the tree, and to saw through two-thirds of the strongest roots.  The opening is then filled in with fresh mould.  Should the growth still be too vigorous, the soil must be opened again the following season and the remaining roots cut through, care being taken not to injure the young fibrous roots.