erica; its management and culture. 
241 
may have, it is as yet generally but little understood; the idea, 
however, of growing on this principle ought not, befoie its 
capabilities are better tested, to be entirely repudiated. My 
impression is, that though a plant may succeed for a time by 
this method, yet that it will be of short duration, and its beauty 
but transient; because a plant shifted from a 60-sized pot to 
that of 16, will, with ordinary success, grow rapidly, and its 
roots reach to the side of the pot horizontally, from whence 
they first emanated, it being seldom, if ever, found that the 
roots of potted plants penetrate perpendicularly, there being 
nothing to attract in that direction. Pots, being composed of a 
porous substance, imbibe the carbon of the air, which, being a 
principal constituent of the food of plants, the spongioles aie 
attracted thither ; it is by these alone that food is supplied, 
and if so, we must presume that the nutritive principle which 
the soil contains, and which is imbibed by the spongioles, must 
be soon exhausted in that portion of the soil near to the side of 
the pot, where invariably the roots are in the greatest abun¬ 
dance, and where they will soon form a thickly interwoven 
mass if kept long in the same pot. A plant, however, will not 
long continue vigorous if it be only supplied with food in a 
gaseous state, though it may exist for a considerable time; and 
this explains why plants will continue growing, but weakly, 
even though left for a very long time in one pot; but when 
taken out, their roots will be found in an exceedingly matted 
state around the side, without one particle of soil amongst 
them ; by removing a portion of this entangled mass, the soil 
appears. When large shifts have been given, the soil in the 
centre appears quite in a recent state, and completely destitute 
of radiculse. We may therefore naturally infer, that plants 
shifted from a very small to a very large pot, cannot long con¬ 
tinue in a healthy condition, as the fertilising constituents are 
extracted from one portion of the soil only; that a quantity of 
inert matter remains in the centre, and this, if not removed for 
a length of time, will become soured, and ultimately kill the 
plant. To grow such heaths as are intended to be kept for 
years, the safest and most certain principle to work upon is the 
progressive system. However, let it not be understood that I 
here recommend very small shifts ; in too many instances this 
not only injures plants, but is a waste of time. I therefore 
