Sunshine, Rain, and Wind 
which one can only realise the perfection after very careful 
microscopic dissection, and by much constructive imagi- 
nation, But it is unfortunately impossible to describe 
either the difficult chemistry of wood and cellulose, or 
the mechanical beauty of the tracheid. 
One other little point should be mentioned in this 
chapter, for it is but seldom noticed anywhere. 
The stems of most herbs and shrubs are not either 
straight or cylindrical. There is usually a zigzag curva- 
ture and a system of indistinct grooves and ridges. 
Where the leaf joins the stem there is often a bold 
sweeping curve at the leaf base, continued as a faint 
elevation down the stem. Where leaves are opposite, 
a ridge joins the bases and is often artistically set off 
by a pallisade of hairs. Leaf veins are often sunk below 
the surface, and lead down to intricate little hollows, 
where the bud is nestling between leaf and stem. 
These sculpturings and ornaments are regulated by 
three distinct and different governing principles. There 
is(1) the mechanical support of the stems, and also (2) 
the protection of the young bud in the hollow or axilla 
of the leaf (the “oxter,” as it is called in Scotland, is 
exactly like the bud axil of many leaves). But there is 
also (3) another intention, which is to utilise rain and 
atmospheric dust. The importance of dust has not been 
realised until quite recently. 
The researches of Mr. Aitken in this country have 
shown that even on the summit of Ben Nevis it is very 
difficult-to get a sample of air with only one dust particle 
per cubic centimetre (.061 cubic inch). When Pasteur, 
on 20th Sept. 1860, attempted to get a sample of germ- 
free air at the Montanvert near Chamonix, he had to 
raise his flask above his head to get rid of body currents 
and breath, then by careful manipulation break off the 
point of the flask, which was then hermetically sealed by 
Ig 
