10 
ANNIVERSARY ADDRESS 
surfaces. Thorns and prickles are common on many stems, branches, 
and leaves, and are often, as in the Labiates, found on the calyx. 
All these appliances are of good service. Many leaves with prickles, 
such as those of the holly, frequently have smooth edges when 
growing on the top and in the more inward parts of a well-grown 
plant, where they would not be touched by grazing animals. 
Thistles are greatly protected, and, in many cases, as in the 
common carline, the prickles of the involucre point downwards 
as well as upwards, thus preventing the access of soft-bodied 
animals. The armament of thistles is very necessary, for when 
crushed they are excellent food for horses and cattle. It is 
generally stated that they will be eaten by donkeys, but my ex¬ 
perience leads me to think that this occurs only under the pressure 
of hunger. The upper flowers of the broad burweed ( Xanthium 
strumarium ) and other plants are protected by the prickly seed- 
vessels already formed by the lower flowers. Drought causes 
many plants to produce spines and thorns which are not found 
when they grow in wet places where they are more out of the 
way of grazing animals. Some plants have similar protection 
when young, but not when they reach a certain height. The 
pear-tree when wild has long thorns which become branches under 
cultivation, and the blackthorns, the thorns of which are so pro¬ 
tective, are believed by some to be wild varieties of our thornless 
plum and damson trees. Many of our sedges and grasses, like 
the matgrass ( Nardus stricta), are so stiff that cattle rarely touch 
them. The rough meadow-grass ( Poa trivialis) when in stalk, and 
the prickly carex {Carex muricata ), are avoided in consequence of 
their roughness. The genus Festuca contains some of our best and 
worst agricultural grasses, and Kerner mentions a species {F. 
alpestris ) which is burnt by the shepherds in the district of Monte 
Baldo owing to its leaves ending in such sharp needle-points that 
grazing animals get their nostrils injured when searching for other 
plants growing with it. Stinging nettles are protected from most 
herbivorous animals, although donkeys will eat them, and cattle 
also when hard pressed for food. Rabbits will bite the leaves and 
stalks to clear their holes, but I have never heard of their feeding 
on them. 
The protection of the leaves and branches by means of thorns 
and prickles in any plant extends also of course to the flower. 
But, as already stated, the entomophilous flower has its special 
dangers. Its nectar is relished by other insects than those suitable 
for its cross-fertilisation. An apterous visitor is likely to have the 
pollen that it is conveying rubbed off by the many objects with 
