BY THE PRESIDENT. 
9 
but also a general effect on tbe nervous system pleasurable or 
otherwise. We cannot therefore be sure that the great influence 
of certain colours on animals is not directly due to such causes. 
But, ridiculous as it may appear, when we consider that the red 
poppy of our fields is distasteful to all grazing animals, we may 
see some explanation of the anger which bulls and occasionally 
cows display at the sight of a red rag. It should be borne in mind 
that very gay flowers have rarely strong odours, so that animals 
might be expected only to detect their presence by the sense of 
smell when comparatively close to them. On the other hand, some 
inconspicuous flowers, like the violet, are very fragrant. White is 
a very observable colour, and the fact that white flowers are often 
highly scented would seem opposed to the theory I am advancing, 
for it may be urged that their powerful scent alone would warn 
animals of their proximity, and that the colour was unnecessary. 
But the effusion of odours of many flowers is intermittent, while 
most flowers which are white require fertilisation by nocturnal 
insects and are only sweet-smelling at night. 
The brilliancy of vegetation is in its flowers. Their primary 
function is the continuation of the species, and plants derive the 
same benefit from their showy petals as many birds from the in¬ 
creased attractions of their plumage during the pairing season. 
Yet the colour of the flower may have for a secondary purpose 
the protection of itself and its plant, just as the long spiral stalk 
of the flower of the female Vallisneria spiralis is not only the 
means of securing the fertilisation of its ovary, but also of placing 
it in safety. Nature nearly always kills more than one bird with 
one stone. 
Protection by means of Appliances. 
The woody tissue of plants is clearly of protective service, and 
the same can be said of the epidermis, which is thicker on the upper 
surface of a leaf than on the lower, and is wanting in those parts 
which are constantly submerged. The upper part of a horizontal 
leaf is more exposed to danger than the lower, and is therefore more 
liable to injury. An examination of the two discloses that the cells 
of the upper surface are packed close together in a vertical position 
with their small ends uppermost, while the cells of the lower 
surface are arranged horizontally, and are generally separated by 
open spaces. This difference in structure is doubtless due to the 
greater exposure to light of the upper surface, the denser cellular 
stratum of which is a protection. In the case of vertical leaves, 
as in the Eucalypti, there is not much difference between the two 
