422 ‘APPENDIX. 
mixes broken picces of free-stone with his soil for heaths, but Devonshire 
entire pebbles are found to succeed better. It is really curious, when 
one of the pebbles laid on the surface of the soil in the pots is removed, 
to see what a mass of slender white rocts have formed beneath it; and 
it is not possible to imagine plants growing with more health and vigour 
The heaths and other straggling-growing plants are aiso trained into 
compact bushes, by tying them down to small green sticks fixed in the 
pots. Thisis done gradually: at first they are only tied loosely, to prevent 
the danger of breaking ; but by degrees they are gradually drawn in, till 
at last they assume the desired shape. » 
Niruas.—Gesneracee N. oblonga is a very beautiful little plant, a 
native of Guatemala, and has a dwarf stem, with hairy fleshy leaves, 
something like a Gloxinia ; the flowers also resemble those of Gloxinia, 
but are much smaller, and of a snowy whiteness. The plants look best 
planted in clusters, and only require greenhouse heat. , 
Prorectinc.—[In the Middle and Northern States, a great many shrubs 
and plants, only partially hardy, are successfully preserved through the 
coldest winters by covering them with straw or bass mats, or by covering 
them with a frame of boards ; it having been found by experience that 
half-hardy plants will endure a great depression of temperature, if they 
are not exposed to sudden rupture of the sap-vessels in thawing. For 
this reason, to the surprise of many persons, tender plants growing in 
shady cold exposures are frequently found in the spring to be quite 
uninjured after a severe winter, while those in a warm southern aspect, 
having been exposed to the sudden and great alternations of temperature 
usual in this climate, are destroyed quite down to the root. The leading 
principle, therefore, in the various modes for the protection of out-of-door 
plants, shrubs, or trees, is founded upon preserving them from the influence 
of the sun, and from the consequent sudden thawing and freezing, rather 
than in endeavouring to retain any warmth by covering them from the 
external cold. 
In covering with straw or mats, (especially im the case of evergreen 
shrubs,) care must be taken not to sheath or bind them tightly about the 
branches, as when this has been done, we have known the branches, and 
sometimes the whole shrub, to be destroyed or stifled for want of air. 
The sheathing should be put on very loosely, and, in the case of low shrubs, 
rough frames, covered with mats, or coarse baskets made for the purpose 
and turned over the whole plant, are the best modes. Beds of carnations, 
and other half-hardy plants, may be very safely protected by a loose 
