The cacti are defended better than the other growths because they have more to lose, and are consequently more subject to attack. And yet there is one notable exception. The crucifixion thorn is a bush or tree somewhat like the palo verde, except that it has no leaf. It is a thorn and little else. Each small twig runs out and ends in a sharp spike of which the branch is but the supporting shaft. It bears in August a small yellow flower but this grows out of the side of the spike. In fact the whole shrub seems created for no other purpose than the glorification of the thorn as a thorn.[7]
The sting of flowers.
Fierceness of the plant.
Tree, bush, plant and grass—great and small alike—each has its sting for the intruder. You can hardly stoop to pick a desert flower or pull a bunch of small grass without being aware of a prickle on your hand. Nature seems to have provided a whole arsenal of defensive weapons for these poor starved plants of the desert. Not any of the lovely growths of the earth, like the lilies and the daffodils, are so well defended. And she has given them not only armor but a spirit of tenacity and stubbornness wherewith to carry on the struggle. Cut out the purslain and the iron weed from the garden walk, and it springs up again and again, contending for life. Put heat, drouth, and animal attack against the desert shrubs and they fight back like the higher forms of organic life. How typical they are of everything in and about the desert. There is but one word to describe it and that word—fierce—I shall have worn threadbare before I have finished these chapters.
Odors and juices.
Saps astringent and cathartic.
We have not yet done with enumerating the defenses of these plants. The bushes like the greasewood and the sage have not the bulk of body to grow the thorn. They are too slight, too rambling in make-up. Besides their reservoirs are protected by being in their roots under the ground. But Nature has not left their tops wholly at the mercy of the deer. Take the leaf of the sage and crush it in your hand. The odor is anything but pleasant. No animal except the jack-rabbit, no bird except the sage hen will eat it; and no human being will eat either the rabbit or the hen, if he can get anything else, because of the rank sage flavor. Rub the greasewood in your hand and it feels harsh and brittle. The resinous varnish of the leaves gives it a sticky feeling and a disagreeable odor again. Nothing on the desert will touch it. Cut or break a twig of the sangre de dragon and a red sap like blood runs out. Touch it to the tongue and it proves the most powerful of astringents. The Indians use it to cauterize bullet wounds. Again no animal will touch it. Half the plants on the desert put forth their leaves with impunity. They are not disturbed by either browsers or grazers. Some of them are poisonous, many of them are cathartic or emetic, nearly all of them are disagreeable to the taste.
The expenditure of energy.
The desert covering.
So it seems with spines, thorns, barbs, resins, varnishes and odorous smells Nature has armed her desert own very effectually. And her expenditure of energy may seem singularly disproportionate to the result attained. The little vegetation that grows in the waste may not seem worth while, may seem insignificant compared with the great care bestowed upon it. But Nature does not think so. To her the cactus of the desert is just as important in its place as the arrowy pine on the mountain. She means that something shall grow and bear fruit after its kind even on the gravel beds of the Colorado; she means that the desert shall have its covering, scanty though it be, just the same as the well-watered lands of the tropics.