from too much moisture, and from frosts, and from the depredations of
insects by various contrivances, as by scales, hairs, resinous
varnishes, and by acrid rinds.

The buds of trees are of two kinds, either flower-buds or leaf buds; the
former of these produce their seeds and die; the latter produce other
leaf buds or flower buds and die. So that all the buds of trees may be
considered as annual plants, having their embryon produced during the
preceeding summer. The same seems to happen with respect to bulbs; thus
a tulip produces annually one flower-bearing bulb, sometimes two, and
several leaf-bearing bulbs; and then the old root perishes. Next year
the flower-bearing bulb produces seeds and other bulbs and perishes;
while the leaf-bearing bulb, producing other bulbs only, perishes
likewise; these circumstances establish a strict analogy between bulbs
and buds. See additional notes, No. XIV.]

[_Viewless floods of heat_. l. 462. The fluid matter of heat, or
Calorique, in which all bodies are immersed, is as necessary to
vegetable as to animal existence. It is not yet determinable whether
heat and light be different materials, or modifications of the same
materials, as they have some properties in common. They appear to be
both of them equally necessary to vegetable health, since without light
green vegetables become first yellow, that is, they lose the blue
colour, which contributed to produce the green; and afterwards they also
lose the yellow and become white; as is seen in cellery blanched or
etiolated for the table by excluding the light from it.

The upper surface of leaves, which I suppose to be their organ of
respiration, seems to require light as well as air; since plants which
grow in windows on the inside of houses are equally sollicitous to turn