474 
PLIKy's IfATUEAL HISTOET. 
[Book XVII. 
incessant quivering of its leaves : while that of the alder is very 
dense, but remarkably nutritive to plants. The vine affords 
sufficient shade for its wants, the leaf being always in motion, 
and from its repeated movement tempering the heat of the sun 
with the shadow that it affords ; at the same time too it 
serves as an effectual protection against heavy rains. In 
nearly all trees the shade is thin, where the footstalks of the 
leaves are long. 
This branch of knowledge is one by no means to be despised 
or deserving to be placed in the lowest rank, for in the case of 
every variety of plant the shade is found to act either as a 
kind nurse or a harsh step-mother. There is no doubt that 
the shadow of the walnut, the pine, the pitch-tree, and the fir 
is poisonous to everything it may chance to light upon. 
CHAP. 19. THE DKOPPINGS OF WATEK EEOM THE LEAVES. 
A very few words will suffice for the water that drops from 
the leaves of trees. In all those which are protected by a 
foliage so dense that the rain will not pass through, the drops 
are of a noxious nature.^" In our enquiries, therefore, into 
this subject it will be of the greatest consequence what will 
be the nature developed by each tree in the soil in which we 
are intending to plant it. Declivities, taken by themselves, 
require smaller^^ intervals between the trees, and in localities 
that are exposed to the wind it is beneficial to plant them 
closer together. However, it is the olive that requires the 
largest intervals to be left, and on this point it is the opinion 
of Cato,^^ with reference to Italy, that the very smallest in- 
terval ought to be twenty-five feet, and the largest thirty: 
this, however, varies according to the nature of the site. The 
olive is the largest^^ of all the trees in Baetica : and in Africa 
— if, indeed, we may believe the authors who say so — there 
are many olive-trees that are known by the name of milliariae,^^ 
92 This is quite a fallacy. Even in the much more probable cases of 
the upas and mangineel, it is not the fact. 
Theophrastus, De Causis, B. iii. c. 8, says, that trees that grow on 
declivities have shorter branches than those of the same kind growing on 
plains, 9^ De Re Rust. c. 16. 
This assertion is doubtful ; at the present day, in Andalusia, the 
palm, the poplar, and many other trees are much larger than the olive. 
^6 " Thousand pounders." This, as Fee remarks, is clearly an exag- 
geration. 
