672 
Analyses of Ashes of Plants. 
evidently appears that, in onr present state of ignorance regarding 
the use of minei'al matter in the plants, the analysis of one, or 
even of several samples of any particular plant, will leave us still 
much in doubt as to the average or ordinary amount and compo- 
sition of its inorganic ingredients, and the extent of deviation to 
which they are liable. 
In the case of wheat, it is true we may well believe that for 
practical purposes the number of analyses performed wUl do away 
with all further doubt as to its mineral composition and require- 
ments, but this amount of labour can hardly be expended on all 
other crops. 
There is another most interesting point to which we would call 
attention very shortly. It is the possibility that the ash of plants 
may in some way be connected with the quantity of water they 
contain. It cannot fail to strike any one as remarkable, that the 
grain, the straw, and the chaff of wheat should contain so vuiiform 
a quantity of water. Why, when they dry to this extent, do they 
not lose any more water ? Why do they not become thoroughly 
dry ? Can the soluble salts of wheat in any way be instru- 
mental in retaining this portion of water ? This is really quite 
possible. 
In carrying out this supposition, we are immediately stopped 
by the fact, that whilst the grain, straw, and chaff contain nearly 
equal amounts of water, they differ most decidedly in the quantity 
of ash. But this is the very circumstance which lends interest to the 
speculation ; for whilst in the grain the silica which performs the 
part of an external covering is very small, in straw and chaff it 
reaches — straw, 63 -89; chaff', 81*22 per cent. (Spec. 46). 
Now, if we deduct this quantity of silica from the total ash of the 
straw and chaff, we shall find that the remainiiiof mineral substances 
connected with the internal vegetable matter are very nearly the 
same as in ihe grain. 
Thus the ash in the grain of Spec. 46 is 1 • 60 per cent. ; the ash 
of the straw, 4-20, consisting of 2 • 68 silica, 1 ■ 52 other bodies ; the 
ash of the chaff, 9 • 45, consisting of 7 ' 68 silica, 1 • 75 other bodies ; 
so that the great dissimilarity in quantity of the ash of the straw 
and chaff, when compared with that of the grain, is dependent on 
the great proportion of silica contained in tlie former, and to this 
silica we ascribe an office quite distinct from the rest of the ash. 
Again, barley and oats, which contain about the same per centage 
of water, aflord much moi e ash when burned than wheat ; but this 
excess is also due to silica; for in Spec. 63 the whole ash is 2 14 per 
cent., consisting of '66 silica, I -48 other bodies; and in Specimens 
65, 67, the produce of 64 and 66, the water increases with the 
proportion of ash. 
We are quite aware thnt our own results furnish exceptions to 
