The spiny leaves of the Holly are unfortunately not nearly strong enough to save it from its enemies. The bark is apparently of a particularly delicious and toothsome nature, for sheep, cattle, and the ubiquitous rabbit are always delighted to destroy the trees.
It has been noticed that wild hollies have at the base very spiny leaves, but that higher up on the tree (above the reach of cattle) the leaves have no spines at all. Sir Herbert Maxwell, in his Memories of the Months,[90] takes up this question. It is best to give the description in his own words:—
"I strolled out along the banks of Tay in that noble woodland which is continuous from Dunkeld to Murthly. Here there are many fine hollies, some on the river banks and cliffs, others on level ground, planted by no hand of man. There was not one of these which did not confirm my observations first made many years ago, and hardly one which did not bear evidence of special growth—not merely as a reaction against pruning or cropping, but as a precaution against any such contingency—so regular and deliberate as to suggest that these trees are something more than unconscious automata.
"Many of these hollies are thirty feet high, with foliage down to the ground. They carry spinous leaves up to a height of three or four feet; above that level all the foliage is absolutely smooth and spineless. One tree rose from the ground in two bare stems, and the lower branches did not reach below the browsing level. But from between the two old stems rose a young shoot about four feet long, clothed throughout its entire length with intensely prickly leaves. This tree was growing in an enclosed wood where cattle could not come; still, roedeer might be about, and the holly armed its young growth at the low level, although the leaders of the old stems, not less vigorous in growth, bore leaves as smooth as a camellia's. I noted one particularly suggestive tree, an unhealthy one. The growth had died back along most of the branches, which stood out bare and dry; but a recuperative effort was in progress; fresh and luxuriant growth was bursting along nearly the whole height of the stem, and the foliage of this was vigorously prickly up to about four feet, and smooth above that height. I noticed many instances of localised prickly growth where boughs, originally above the browsing level, and clothed with spineless leaves, had been weighed down and cropped by cattle. But this is merely a vigorous reaction against external injury, such as makes a clipped holly hedge bear spinous foliage from base to summit."[91]
This quotation shows that there is no doubt as to the facts. It is true that one finds cultivated hollies showing many variations. Sometimes all the leaves are spiny, both above and below. In other varieties none of the leaves possess spines at all. Yet it must be admitted that these are facts and cannot be denied.[92]
Moreover, the Osmanthus, with its holly-like leaves, the Evergreen Oak, and some Junipers are found to show exactly the same curious difference. The perilously-situated lower leaves are more spiny than those which are above the reach of grazing animals.
Kerner von Marilaun[93] also has remarked a similar protective arrangement in Gleditschia chinensis and in the Wild Pear. Trees of the latter, when they are young, "bristle with the spines into which the ends of the woody branches are transformed"; but tall trees twelve to fifteen feet high are entirely without thorns!
It is when one meets coincidences of this nature that the full meaning of plant life begins to dawn upon the mind.
How is it that the plant knows the time to produce its spines, and the time to refrain from doing so?
There are certain queer facts that have been given on good authority as to the causes which tend to produce thorniness and spininess.