In Greenhouses.—­For the greenhouse proper, Cactuses are well adapted, either as the sole occupants or as suitable for such positions as are afforded by shelves or baskets placed near the roof glass.  If the greenhouse is not fitted with heating arrangements, then, by selecting only those species of Cactus that are known to thrive in a position where, during winter, they are kept safe out of the reach of frost (of which a large number are known) a good collection of these plants may be grown.  In heated structures the selection of kinds may be made according to the space available, and to the conditions under which they will be expected to grow.  Fig. 3 represents a section of a house for Cactuses, which will afford a good idea of the kind of structure best suited for them.  The aspect is due south.

[Illustration:  Fig. 3.  Section of house for cactuses—­A,A, Hot-water Pipes; B,B, Ventilators.]

When grown on their own roots, the Epiphyllums, as well as the pendent-growing kinds of Rhipsalis, and several species of Cereus, may be placed in baskets and suspended from the roof.  The baskets should be lined with thin slices of fibrous peat, and the whole of the middle filled with the compost recommended for these plants under “Soil”.  When well managed, some very pretty objects are formed by the Epiphyllums grown as basket plants.  The climbing Cactuses are usually planted in a little mound composed of loam and brick rubble, and their stems either trained along rafters or allowed to run up the back wall of a greenhouse, against which they root freely, and are generally capable of taking care of themselves with very little attention from the gardener.

In Frames.—­For cultivation in frames, the conditions are the same as for greenhouses.  Even when grown in the latter, it will be found conducive to the health and flowering of the plants if, during the summer months, they can be placed in a frame with a south aspect, removing them back to the house again on the decline of summer weather.  Wherever the place selected for Cactuses may be, whether in a large plant-house, or a frame, or a window, it is of vital importance to the plants that the position should be exposed to bright sunshine during most of the day.  Without sunlight, they can no more thrive than a Pelargonium could without water.  In Germany, many growers of almost all the kinds of Cactuses place their young plants in frames, which are prepared as follows:  In April or May a hot-bed of manure and leaves is prepared, and a frame placed upon it, looking south.  Six inches of soil is put on the top of the bed, and in this, as soon as the temperature of the bed has fallen to about 70 deg., the young plants are placed in rows.  The frames are kept close even in bright weather, except when there is too much moisture inside, and the plants are syringed twice daily in dry, hot weather.  The growth they make under this treatment is astonishing.  By the autumn the plants are ready to be ripened by exposure to sun and air, and in September they are lifted, planted in pots, and sent to market for sale.  This method may be adopted in England, and if carefully managed, the growth the plants would make would far exceed anything ever accomplished when they are kept permanently in pots.