230 
HABITS OF PLANTS — SEASON OF REPOSE. 
saturated with strong salt brine ; strain this against the face of a strip of well 
planed oak-board eighteen inches long, and fasten each end to two brass- headed 
nails, so that the string be tight while wet. To the board let another piece of the 
same wood be fixed, and at right angles with and below it, like the drawing-master's 
cross-shaped square. This strip of wood need not be above six inches long, and to 
it is to be pasted a piece of paper graduated as a scale of equal parts, to be determined 
by the expansion of the salted line when made perfectly dry before the fire. A 
silk line fastened to the middle of the cord, having a large shot attached to the end 
of it, will serve as an index at all times ; and at the season alluded to, when a 
vaporous atmosphere prevails, the salted cord will contract and become so tight, as 
to raise the weight to its upper limit marked zero — 0. This instrument, which was 
figured some months ago in the Gardeners' Chronicle, is extremely sensitive ; it 
marks the slightest variations of moisture in a house, even those occasioned by a 
passing cloud over a bright and powerful sun. It also proves how extremely difficult 
it is to maintain vaporous saturation during the existence of actual sunshine. 
Having the means at command to ascertain with a degree of accuracy the 
moisture of any plant-house, we are in a position to investigate the habits of the 
plants usually cultivated in large establishments, and to arrange them under several 
heads. Not, however, to indulge too much in minutise, we will restrict these to five, 
namely : — 
1. Plants of the Orchid tribe, Orchidacece — Orchids. 
2. Plants whose organisation is strictly succulent. 
3. Plants, miscellaneous in structure, natives of warm climates, and therefore 
always requiring heat — Stove plants. 
4. Plants not absolutely tender, but requiring protection and impatient of 
moisture. 
5. Greenhouse plants of the hard- wooded families. 
As this investigation refers entirely to the treatment which is indicated by the 
approach of winter, it will be needless to take any particular notice of the various 
erections in which the subjects are deposited ; each will, therefore, be considered as 
a separate and individual planthouse. 
I. The Orchids. — These plants, by the peculiarities of their organisation and 
natural situations, plainly indicate that their abode must be select, and their mode 
of treatment arbitrary. Orchids are divided into two distinct classes, the Epiphytal 
and the Terrestrial. The former grow upon trees in the tropical forests of Asia and 
South America. " They establish themselves upon the branches, and either vegetate 
amidst masses of decayed vegetable and animal matter, or cling by their long roots 
to the naked wood, from which, and the humid atmosphere, they exclusively derive 
their food." Great heat, a vaporous atmosphere, and deep shade, therefore, are 
the elements of their life. 
The terrestrial Orchids, on the contrary, require a little soil, such as the earth of 
decayed mosses and wood, and fibrous heath-soil, interspersed with pieces of broken 
