On the Physiology of Vegetables. 347 
fix the dust and dirt on them ? would not the drops thicken and 
agglutinate, and run over the plant, marking it with stripes of 
dirt and filth? Ifthe drops issued from the leaves, could the 
dust be blown off as it may, leaving the plants shining and beau- 
tiful,and its vivid green such as to delight the eye and vivify the 
heart ? Conceive how different Nature would appear : How lovely 
is the clear animated green in spring, when the delicacy of the 
colour is such as would exhibit every ‘defilement¢ ; and yet, even 
in dusty roads the trees soon throw off, by their motion (and 
the constant action of the spiral wire) that dust which op- 
presses them, and which the wind helps to disperse:—we are lit- 
tle aware how many iinportant avocations of Nature would be 
stopped by such a perspiration. It is the leaves which receive 
the nutriment from the atmosphere:—but if that defilement re- 
mained glued on the leaves, how could they take it in? it would 
be absorbed by the dirt;—and what then is all that beautiful glit- 
tering net that covers many leaves,—what that waxy covering so 
conspicuous in all evergreen leaves >—How will that agree with 
perspiration ?—But it is in vain to pursue a theme where all the 
reasons are on one side alone, and no answer is made but a sim- 
ple No. Would a plant in-doors collect dust like any other fur- 
niture, and that dust be blown or brushed off with a feather ? 
No, it would stick to the leaves. Every one knows what the 
honey-dew is, though formed by insects which conceal a few 
eggs in each glutinous bubble; yet it has in reality exactly the 
effect that would ensue if leaves ‘perspired ; for being a parcel of 
glutinous balls, they collect the dirt and dist, and the dampness 
of the Jeaves covers them with a sort of black Cryptogamia, and 
the whole plant soon becomes disgusting to the sight, and ex- 
actly the same as all plants would be if they perspired. 
I am, sir, your obliged 
—— AGNEs IBBETSON. 
-P.S. It may also be easily proved that that visible perspiration 
talked of, and found now and then on a few trees—and which 
I have for the third time thoroughly examined this year,—is the 
transparent egg of a small insect, which is at the time feeding 
under the leaf, while the eggs are left on the upper surface. It 
is really a matter worth watching—for they have a phenomenon 
observable, (I believe, just before the insects make their appear- 
ance,) which well deserves being examined. it is a most asto- 
nishing rotatory motion in the eggs, which running round with 
great velocity continue to do this for above a minute at a time ; 
nor was it when the mother insect was near: J have shown it 
to many. 
De- 
