One of the greatest difficulties attending the culture of plants in a bark stove is, guarding against the ravages of the immense number of insects that are engendered by the heat; and one of the most troublesome of these is the active little mite called by gardeners the red spider (_Àcarus telùrius_). This little pest breeds in the bark, and when first hatched it is so small as to be scarcely perceptible; particularly as it is of a pale green, nearly the colour of the under side of the leaf, to which it fixes itself, and there spins a web. As it gets older it becomes of a brownish red, and having eight legs, it runs with the greatest rapidity. It is also furnished with a proboscis, with which it sucks the juices of the leaves, making them wither and shrivel up; and thus the flowers and the fruit of the trees are both spoiled, as neither can attain perfection unless the sap that is to nourish them be first properly matured in the leaves. Tobacco smoke, and most of the other usual remedies against insects, have no effect on the red spider; and, though sprinkling it with very cold water will kill it, it is difficult to apply without injuring the plants. The best remedy is allowing plenty of air to pass through the house, whenever the weather is hot enough to allow the atmospheric air to be admitted with safety. The culture of the plants contained in the _dry stove_ requires considerable care. The Cáctus family may be arranged in three groups; first, the Tree Cacti, which are included in the genus Cèreus, and have long slender stems without a single leaf, sometimes thirty or forty feet high, and not thicker than a man's arm. These plants grow on the summits of the mountains in Brazil, and only require greenhouse heat in England. Secondly, the Mammillàriæ and Echinocácti, which grow in the valleys of the temperate parts of South America, and should be kept in a warm greenhouse in this country; and thirdly, the Melocácti, the Epiphýllum, the Opúntiæ, and the Rhípsalis, which grow in the tropics, and require a dry stove in England. These plants should be grown in pots well drained with cinders, and they should be kept almost without water from October till March, and then watered profusely till they are about flowering, when the quantity of water given to them should be gradually diminished. Some cultivators keep a few of their plants in a bark stove, and plunge the pots in the tan, and they are said to thrive on this treatment, if carefully managed; but as it requires a great deal of care to prevent them from damping off, the ordinary way is the safest for an inexperienced gardener. Mesembryanthemums, which are also kept in a dry stove, require the same treatment as the Cácti.