both in size and form of the stem and in the flower characters of the different species.  A large proportion of the 200 kinds known are not cultivated in European gardens, and perhaps for many of them it is not possible for us to provide in our houses the peculiar conditions they require for their healthy existence.  But there are a good many species of Cereus represented in gardens, even in this country, and among them we shall have no difficulty in finding many useful and beautiful kinds, such as may be cultivated with success in an ordinary greenhouse or stove.  Lemaire, a French writer on Cactuses, groups a number of species under the generic name of Echinocereus; but as this name is not adopted in England, it is omitted here, all the kinds being included under Cereus.

The night-flowering species.

The most interesting group is that of the climbing night-flowering kinds, on account of their singular habit of expanding their flowers in the dark and of the very large size and brilliant colours of their flowers.  In habit the plants of this set are trailers or climbers, their stems are either round or angled, and grow to a length of many feet, branching freely as they extend.  By means of their roots, which are freely formed upon the stems, and which have the power of attaching themselves to stones or wood in the same way as ivy does, these kinds soon spread over and cover a large space; they are, therefore, useful for training over the back walls in lean-to houses, or for growing against rafters or pillars—­in fact, in any position exposed to bright sunlight and where there is a good circulation of air.  Soil does not appear to play an important part with these plants, as they will grow anywhere where there is a little brick rubble, gravel, or cinders for their basal roots to nestle in.  They have been grown in the greatest luxuriance and have produced flowers in abundance with nothing more than their roots buried in the crumbling foundations of an old wall, upon which the stems were clinging.  The chief consideration is drainage, as, unless the roots are kept clear of anything like stagnation, they soon perish through rot.  During the summer, the stems should be syringed morning and evening on all bright days, whilst in winter little or no water will be required.

Like all other Cactuses, these plants may be propagated by means of large branches, which, if placed in a porous soil, will strike root in a few weeks.  We saw a very large specimen of C. triangularis, which last autumn suddenly rotted at the base, from some cause or other, and to save the specimen, a mound was built up of brick rubble and soil, high enough to surround the base of the plant above the rotted part.  In a few weeks there was a good crop of new roots formed, and the plant has since flowered most satisfactorily.  With almost any other plant, this course would have proved futile; but Cactuses are singularly tenacious of life, the largest and oldest stems being capable of forming roots as freely and as quickly as the young ones.