Cistus (Rock Rose).—­A compost of loam and peat suits these beautiful evergreen shrubs.  They may be increased by layers, ripe cuttings covered with a hand-glass, or seed.  Though the plants are pretty hardy it is advisable to afford them protection during severe frosts.  June is their flowering month.  Height, 3 ft. to 6 ft.

Citrus Japonica.—­A greenhouse evergreen tree, requiring a rich loamy soil.  Very little water should be given it while in a growing state.  It is generally budded on an orange or lemon tree and plunged in a bottom-heat.  June is its flowering season.  Height, 5 ft.

Cladanthus.—­The annuals may be sown in the open in April to flower in July.  The greenhouse evergreens may be propagated by cuttings under glass.  These produce flowers in June.

Clarkia.—­These hardy annuals make a pretty display in the borders during summer.  Seed ripens plentifully, and merely requires sowing in the open in March, or in September if protected in winter.  The bloom lasts from June to September.  Height, 18 in.

Claytonia Sibirica.—­A hardy herbaceous plant which yields light yellow flowers in June.  It is not particular as to soil, and may be raised from seed sown either in autumn or spring.  It stands division of the root.  Height, 4 ft.

Clematis (Virgin’s Bower).—­These plants like a dry situation.  They will grow in smoky districts, and may be increased by cuttings of firm side-shoots under a glass in summer or by layers in September.  With the protection of a greenhouse they come into flower early in spring.  They are the most beautiful of all flowering hardy climbers.  The stove and greenhouse varieties are best planted in loam and peat, though they will thrive in any light soil.  Any good garden soil suits the hardy kinds.  The herbaceous varieties are increased by dividing the roots early in spring.  They bloom at various periods.  After they have ceased to flower, the Jackmanni and Viticella sections should be cut down to within 9 or 12 in. of the ground.  The Patens and Florida do not require pruning; those of the Lanuginosa should be cut back moderately, but not too close.  A good dressing of leaf-mould and manure should be dug in about November.  Heights vary from 2 ft. to 20 ft. (See also “Traveller’s Joy.”)

Cleome.—­The species of this genus are very pretty and free flowering, some being half-hardy climbers notable for their foliage.  They like a rich, light soil.  Cuttings of the stove kinds root freely under a glass.  Some of the annual species require to be sown in a hotbed frame or in a hot-house, then potted off and placed with tender annuals.  The hardier ones may be sown on a hotbed, and afterwards planted out in a sheltered position.  They flower in May, June, and July.  Heights vary from 6 in. to 8 ft.

Clethra Alnifolia.—­This hardy deciduous shrub bears in September deliciously scented pure white flowers on the side-shoots of the previous year’s growth.  It needs a light soil and a dry, sunny situation.  It may be propagated by cuttings placed under glass in sandy loam, or by suckers taken when the leaves have fallen, but is more generally increased by layers.  Height, 3 ft.