Colchicum (Autumn-Flowering Crocus).—­Plant the bulbs in February in light, loamy soil, placing them 2 in. deep and 3 in. apart.  They are readily increased by off-sets from the bulb.  September is their flowering season.  Height, 3 in. (See also “Bulbocodium.”)

Coleus.—­Tender perennial shrubs of some merit, requiring the protection of a greenhouse.  Keep the plants root-bound and near the glass, with a good supply of heat and moisture.  They succeed best in a mixture of loam and peat.  Cuttings of shoots 3 in. long planted in sand, covered with a glass, and plunged in heat 60 to 70 degrees, will strike.  Pot off singly in loam and sand.  Bloom in June or July.  Height, 2 ft. to 3 ft.

Colletia.—­Ornamental evergreen shrubs.  A mixture of peat and loam, with a sheltered position, is their delight.  Cuttings will strike in sand if covered with glass.  They produce their flowers in July.  Height, 2 ft. to 3 ft.

Collinsia.—­Most elegant hardy annuals, doing well in any garden soil.  The seed is sown in autumn for early flowering, and in spring for a later display.  Bloom May to August.  Height, 1 ft.

Collomia.—­Hardy annuals, possessing little beauty.  Treat as Collinsia.  Flower in July.  Height, 1 ft. to 2 ft.

Colt’s-foot.—­This hardy perennial flowers before the leaves appear.  It grows best in a moist, clayey soil, and may be increased by pieces of the running root.

Columbine.—­See “Aquilegia.”

Colutea Arborescens (Bladder Senna).—­A shrub with Acacia-like leaves and producing yellow Pea-shaped flowers in July, followed with bladder-shaped seed vessels.  It will grow in any soil, and may be raised either from seed or cuttings taken in autumn.  Height, 10 ft.

Commelina Sellowina (Blue Spider Wort, or Day Flower).—­A pretty greenhouse climber, bearing cobalt-blue flowers.  It should occupy a sunny position, and be watered freely from March to September, after which very little should be given.

Commelina Tuberosa.—­Perfectly hardy plants, bearing in June blue or white flowers the size of a shilling.  The bulbs may be planted in spring in any garden soil; the plants are increased by off-sets.  Height, 1-1/2 ft.

Compost Heap.—­Get a heap of dead leaves and press and jam them down as closely as possible.  Then take as much manure, in appearance, as you have dead leaves, and for each cartload have two bushels of unslaked quicklime and some earth.  Now spread upon the ground, in some out-of-the-way corner, a layer of the dead leaves, upon which sprinkle a layer of lime, and over that a thin layer of earth.  Next lay on a covering of manure, then a layer of leaves, and one of lime and earth as before, and proceed in this way till all the materials are used up.  It will be well, however, to give the heap a good watering whenever you come to the layer of leaves.  This slakes the lime and hastens the decomposition of the