Furure Bovranist. 13 
or by an expanded leaf-stalk. Stipules are probably useful in 
other ways, ¢.g., in conducting rain down the stem. 
Hairs are found very commonly in Nature, and are used for 
all sorts of purposes. The most important is probably to guard 
against excessive loss of water by transpiration. In the Sahara 
Desert the prevailing tint of the landscape is grey, not green as in 
our own country, because almost all the shrubs are covered with 
erey and silvery hairs. This also occurs in Europe in exposed 
situations. The Hdelweiss growing on wind-swept rock ledges 
is densely white and silvery, so is the Alpine Ladies’ Mantle. 
These plants cover themselves with cotton-wool to keep the 
moisture in just as we use clothes to keep the rain out. An 
instance of this is found in our Alpine Chickweed, found at 
Black’s Hope, &c. This chiefly differs from the common species 
by beng more woolly and having larger flowers. We can in this 
case guess how this species may have arisen, for a variety 
(alpestre) of the common ec. triviale, which I found to be common 
on Whitcoomb and Auchencat in 1892, is both more hairy and 
larger flowered than is usual, and so approaches the Alpine form. 
There is even a good deal of evidence on hand to show that hairs 
disappear when such exposed plants are cultivated in moist and 
sheltered places. I have found this myself in a desert plant which 
i grew in a greenhouse, and which lost its hairs in that situation. 
Something of the same kind is found in Polygonum Amphibium, of 
which land forms are viscous and hairy, while water forms are quite 
smooth. In this species the hairs are probably of use in guarding 
against insects. It is said that hairs occasionally absorb moisture, 
but this cannot be considered proved. I have already alluded to their 
use as protection against insects; a good example is the character- 
istic downward-pointing hairs of the Forget-me-not. The sting- 
ing hairs of the nettle prevent human beings from injuring its 
brittle stems, and the hairs of the white deadnettle, as well as the 
plant generally, are so similar that the latter enjoys the same pro- 
tection. In other cases they are utilized for climbing or the dis- 
tribution of seeds, as, ¢.g., in the goose grass and other Galiums. 
The Sundew uses modified hairs to catch insects. In the Chick- 
weed they are used to conduct water down the stem, and so on. 
The modifications of the stem are scarcely so well known; 
plants are annual and perennial as a matter of convenience. The 
former are most common where there is a distinct check to vege- 
