Remove the danger which threatened the extinction of a family, and immediately Nature removes the defensive armor. On the desert, for instance, the yucca has a thorn like a point of steel. Follow it from the desert to the high tropical table-lands of Mexico where there is plenty of soil and moisture, plenty of chance for yuccas to thrive, and you will find it turned into a tree and the thorn merely a dull blade-ending. Follow the sahuaro and the pitahaya into the tropics again, and with their cousin, the organ cactus, you will find them growing a soft thorn that would hardly penetrate clothing.
But are they not just as much exposed to browsing animals in the high table-lands as in the desert, if not more so?
Mr. Van Dyke asserts that Nature is more solicitous about the species than about the individual. She is no more solicitous about the one than the other. The same conditions apply to all. But the species are numerous; a dozen units may be devoured while a thousand remain. A general will sacrifice many soldiers to save his army, he will sacrifice one man to save ten, but Nature's ways are entirely different. Both contending armies are hers, and she is equally solicitous about both. She wants the cacti to survive, and she wants the desert animals to survive, and she favors both equally. All she asks of them is that they breed and multiply endlessly. Notwithstanding, according to Van Dyke, Nature has taken such pains to protect her desert plants, he yet confesses that, although it seems almost incredible, it is nevertheless true that "deer and desert cattle will eat the cholla—fruit, stem, and trunk—though it bristle with spines that will draw blood from the human hand at the slightest touch."
This question of spines and thorns in vegetation is a baffling one because Nature's ways are so unlike our ways. Darwin failed utterly in his theory of the origin of species, because he proceeded upon the idea that Nature selects as man selects. You cannot put Nature into a formula.
Behold how every branch and twig of our red thorn bristles with cruel daggers! But if they are designed to keep away bird or beast from eating its fruit, see how that would defeat the tree's own ends! If no creature ate its little red apples and thus scattered its seeds, the fruit would rot on the ground beneath the branches, and the tribe of red thorns would not increase. And increase alone is Nature's end.
It is safe to say, as a general statement, that the animal kingdom is full of design. Every part and organ of our bodies has its purpose which serves the well-being of the whole. I do not recall any character of bird or beast, fish or insect, that does not show purpose, but in the plant world Nature seems to allow herself more freedom, or does not work on so economical a plan. What purpose do the spines on the prickly ash serve? or on the thistles? or on the blackberry, raspberry, gooseberry bushes? or the rose? Our purple-flowering raspberry has no prickles, and thrives as well as any. The spines on the blackberry and raspberry do not save them from browsing cattle, nor their fruit from the birds. In fact, as I have said, the service of the birds is needed to sow their seeds. The devil's club of Alaska is untouchable, it is so encased in a spiny armor; but what purpose the armor serves is a mystery. We know that hard conditions of soil and climate will bring thorns on seedling pear-trees and plum-trees, but we cannot know why.
The yucca or Spanish bayonet and the century-plant, or American aloe (Agave americana), are thorny and spiny; they are also very woody and fibrous; yet nothing eats them or could eat them. They are no more edible than cordwood or hemp ropes. This fact alone settles the defense question about spines.
V. SEA-DOGS
There is a bit of live natural history out here in the sea in front of me that is new and interesting. A bunch of about a dozen hair seals have their rendezvous in the unstable waves just beyond the breakers, and keep together there week after week. To the naked eye they seem like a group of children sitting there on a hidden bench of rock, undisturbed by the waves that sweep over them. Their heads and shoulders seem to show above the water, and they appear to be having a happy time.
Now and then one may be seen swimming about or lifted up in a wall of green-blue transparent water, or leaping above the wrinkled surface in the exuberance of its animal spirits. I call them children of the sea, until I hear their loud barking, and then I think of them as dogs or hounds of the sea. Occasionally I hear their barking by night when it has a half-muffled, smothered sound.