REMARKS ON THE GENUS HOY A. 
13 
it is said, (^Farmer's Magazine^ 1815,) may be heated to 120 degrees. By the 
aeration of" lands in winter, minute mechanical division is obtained by the freezing- 
of the water in the soil ; for as the water in the solid state occupies more space 
than when fluid, the particles of earthy matters, and of decomposing stones, are 
thus rent asunder, and crumble down into fine mould." 
10. Soils may he improved hy adding to, or suhtraetingfrom them, ingredients 
in ivhicJi they are deficient, or superahound. If a soil, of good appearance and 
texture, contain sulphate of iron, it may be ameliorated by quick lime ; if there be 
excess of calcarious matter, it may be improved by the application of sand or clay» 
Soils too abundant in sand are benefited by the use of clay, marl, or vegetable 
matter. 
By burning soils considerable chemical changes can be brought about. " The 
bases of all common soils are mixtures of the primitive earths and oxide of iron, 
and these earths have a certain degree of attraction for each other." " When clay 
or tenacious soils are burnt, they are brought nearer to a state analogous to that of 
sand. In the manufacture of bricks, the general principle is w ell illustrated : if a 
piece of dried brick earth be applied to the tongue, it will adhere to it very strongly, 
in consequence of its power to absorb water ; but after it has been burnt, there will 
scarcely be any sensible adhesion." 
" The soils improved hy hurning are all such as contain too much dead 
vegetable fibre ; also, all such as contain their earthy constituents in an impalpable 
state of division, that is, stiff clays and marls ; but in coarse sands and rich soils, 
containing a just mixture of the earths, and in all cases in which the texture is 
sufficiently loose, or the organisable matter sufificiently soluble, the progress of 
burning cannot be useful." — Domestic Gardener s Manual, 
REMARKS ON THE GENUS HOYA, 
AND PARTICULARLY UPON HOYA CARNOSA. 
We beg to refer the reader to page 26 of the second volume : therein we have 
noticed many of the leading features which characterise the natural order 
AsclepiddecB. This order is well defined, its subjects are remarkable, their 
botanical structure very curious, and, in many instances, they possess great beauty. 
The genus Iloya is found in the Linnsean fifth class, Pentandria ; in the 
second order, Digynia ; the stamens, therefore, are five, and the pistils, or styles, 
two: the natural characters are flowers, monopetalous, inferior ; fruit superior being 
a follicle, or leaf-like capsule. Herein all the Asclepiddece agree, the genera of 
which are numerous. The essential characters of Hoya are a five-cleft corolla. 
The masses of pollen (which might be mistaken for anthers) fixed at their bases 
converging upwards ; stigma depressed, with an obtuse wart ; follicles smooth ; 
seeds smooth. 
These minutiae are not traceable, unless by dissection ; for the reproductive 
