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VEGETABLE PHYSIOLOGY. VT 
a compost suitable for the plants at any stage of their growth. No doubt by selecting established 
cuttings in spring, large plants may be gl■o^^^l by a continuance through the summer of the 
stopping and shifting processes : and such plants, from the free-flowering habit of the species, 
will probably be found extremely useftd for late autumn and winter flowering in a waim con- 
serTator}^ Yoimg plants thus managed would also no doubt in any case be found preferable to 
older cut doT^^l plants, in so far as healthy gi-owth and yigorous blossom-heads were concerned. 
From memoranda commimicated by Mr. Brown, the foreman at Messrs. Eollisson's niu'sery, 
we learn that plants gi'owing in sixty-sized jjots, will carry a fine head of bloom, and as these 
may be had in flower in the winter and eaiiy spring, they must in that state be esjDecially 
valuable for the decoration of di-awing-rooms or conservatories, or for gTouping and massing 
with other plants in ornamental vases. Probablj' this is the form in which the species will be 
fovmd most useftd to cultivators, as its ageratum-like appearance will perhaps cause it to be less 
prized during the summer months. Plants for this piu'pose shoidd be struck and well-estabhshed 
in their pots early in autumn ; and may then be had in succession, by keeping back the principal 
stock as much as possible in a low temperature, and placing a selection, fi-om time to time in a 
more exciting atmosphere. From 60 to 70 degrees appeal's to be the range of temperatui-e suited 
to the growth of the plants, according to the experience already acquired ; and 65 degrees, with 
a dry atmosphere, woidd therefore suit them when at rest. — M. 
i'ttgttnlilt ^Mjtjsinlngti. 
By AUTHUR HENFRET, Esa., F.L.S., Lecturer on Bot.vky at St. George's Hospital. 
CHEMICAL ACTION. 
®OME knowledge of the characters of chemical force, and of the mode in which chemical laws act, 
5^ is indispensable for the comprehension of the phenomena presented in the fives of vegetables. 
Plants stand midway between the dead mineral world and the active, moving portion of the U\'ing 
world, the animal kingdom, in the gTeat chemical interchange wliich is constantly takuig place 
between the several portions of the material creation. Both animals and plants are constructed 
and built up of substances derived from the earth, an-, and water ; but vegetables alone are capable 
of receiving these nuneral materials into the substance of their structures, and of assimilating them, 
as it is caUed — that is, of making use of them as food out of which thefr existing pai-ts may be 
repau-ed and strengthened, and new parts produced. Anim als cannot obtain nourishment fi-om 
any substance which has not pre^dously formed part of a vegetable ; and in the vegetable kingdom, 
therefore we find the most remarkable of those natural phenomena in which the chemical and 
vital forces act together. The whole vegetable kingdom nfight indeed be regarded, in an utUitarian 
point of view, as a great apparatus for the production of organic substances, that is, of chemical 
compounds, difi'ermg fi'om aU those we can om'selves produce at wiU in our laboratories, in so far 
that they can be formed only in the interior of the tissues of fiving things, by chemical action 
regulated and du-ected by the special vital force of the being of which they form pai't. 
In the formation of these compoimds within plants, the general chemical laws still hold good, and 
the chemical action in plants is not dfiferent, but only more complex than in the mineral kingdom ; 
this complexity arising fi-om the interference of the new agent, fife, in the phenomena. So greatly, 
however, does this influence the character of the chemical actions, that we find the resulting com- 
pound formed fi-om a few of the simple elements, multipfied a thousandfold under its direction ; and whfie 
in the mineral world we see a certain product always formed when we unite two given substances 
together, when we place two, ten, or a hundi-ed plants in such a position that they are aU deriving 
the nourishment from the same soil, we find the same set of elements entering into all, but almost 
evei-y species forming some new and different product fi-om them in one or other pai-t of its tissues ; 
and, moreover, the formation of these products depends ahnost wholly upon the degree of health or 
■vital power of the plant. Hence the almost innumerable variety of vegetable substances, the oils, 
acids, alkaloids, &c. : afi consisting of almost the same elements, few in number, which, in their free 
state, when not under the dh-ection of a vital force, are only capable of uniting into a comparatively 
small number of compounds. 
The use of the word element recalls me to the immediate subject of the present paper, namely, a /^ 
^ ^ „ lls^ 
