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the most arid tracts, and serves to give a somewhat stimulating property to the atmosphere. This odor is due not only to the abundance of artemisias, but to a great variety of plants, especially those of the Labiate order, such as species of Salvia and Audibertiæ. Most of the Compositæ found here are more or less aromatic. In all cases the aroma seems to depend upon a resinous exudation, which probably performs the office of checking evaporation, by closing the pores of the leaves, and thus enables the vegetation of these arid tracts to survive the long continued dry season.
The effect of the peculiarities of the climate upon the vegetation of this region may be noticed here. The singular alternations of wet and dryness, heat and cold, produce a confused blending of seasons. Upon the immediate coast most of the annuals and those perennial plants having a succulent nature make their growth during the winter months, that being the season of rain.
In this latitude vegetable growth meets with but very little impediment from cold, as in these months the temperature rarely falls below the freezing point. When the Novemcer rains commence falling vegetation puts on its spring aspect, every barren hill is soon clothed in green, and by midwinter flowers are blooming in profusion everywhere, and many have even passed their brief season and have gone to seed. At this time the larger trees and deciduous shrubs drop their leaves, and only resume them at the close of the rainy season. This seeming exception to the general activity of vegetable life during the winter months is accounted for by the fact that the class of plants alluded to is almost exclusively confined to the margins of streams, hence their growth depends less upon moisture from the atmosphere. As dryness advances, during the months of May and June, all the evanescent forms are swept away, and the profusion of spring flowers gives place to the scanty products of the arid summer. Finally, these two yield to a still more sparse autumnal growth, which is mainly confined to the courses of streams. On the mountains, however, we find the alternation of seasons more like that of temperate climates. Here there is a winter sufficiently cold to prevent and a summer sufficiently moist to favor vegetable growth, which continues throughout the latter season. The scanty vegetation
uncertain showers of summer, and depends mainly upon the regular overflowing of the river. As the waters recede, the inundated places are speedily covered by a very rapid growth.
An enumeration of the plants observed, with precise and detailed accounts of the most interesting among them, will be found in the accompanying memoir by Professor John Torrey.
We will conclude this general sketch by briefly considering the agricultural capacities of the country, as indicated by its general geological features, its climate, and the natural botanical productions.
Commencing at the coast, we notice a prominent wall of high tertiary stuff abutting on the sea. This portion, which is thinly clad with verdure at any season, presents an uninviting aspect. Hence it happens that to the traveller who views it from the sea it is forbidding in the extreme. At a variable distance inland, however, where we find the line of settlements, the rounded hills are covered with a deep rich loam, which in the spring produces a luxuriant crop of wild oats. The river margins of this section are also of the same fertile character, and
support a rank vegetation. Along this belt, too, lie fruitful plains, which, when clothed with the pasturage of early spring, excite the admiration of the beholder.
As we approach the junction of the tertiary and the granitic exposures barrenness again prevails. The thin soil, which is here confined to the crevices of the rocks, produces a growth of shrubbery, the stunted character of which indicates its unproductive nature. Proceeding further inland, we find among the basin-shaped mountain valleys large trees and rich pasture grasses, denoting that a fertile soil again appears. This character, more or less varied by local causes, extends to the summit level.
Occasionally terraces are found upon the higher mountain slopes which possess a productive clay soil, well adapted to the growth of winter grains. In general, however, these localities are rugged and barren. From these facts it woull appear that this country possesses a large share of fertile soil, but in estimating its agricultural capacities we must also take into consideration the peculiarities of the climate if we would arrive at correct conclusions. It is owing to the fact that this latter is not taken into account that such discrepancies occur in the statements of travellers, who, according to the season at which they view the country, pronounce it sometimes a desert and at others a garden. Let any one follow up the coast in the month of March, and pass over the verdant plains that stretch towards the sea ; let him see every valley and hill clothed in the rich green of the wild oats, and every snow-fed stream running with clear water, and he will exclaim, “ This is Arcadian land, the realization of the poet's song.” But let him pass over the same region in the month of August or September, when nearly every green thing has disappeared, when, instead of soft breezes wafting over refreshing verdure, the heated air rises with a wavy tremor from the parching ground ; let him visit the land when nothing remains of the streams but the dry beds, and the herds of cattle, which before were roaming at large in the enjoyment of the rich pasturage, are gathered in herds around the margins of the stagnant marshes, and the same traveller will pronounce the country to be a desert unfitted for the abode of man or beast.
Here, then, we have two widely differing extremes, between which lies the proper mean.
The true mode, then, of estimating how far this region is adapted to agriculture is to follow up the courses of the various streams which run towards the sea, and note the point at which the supply of water is constant, the width of the valley, and the nature of the soil at these places, and also whether the character of the surface will admit of irrigation. We then have the data for forming a just opinion as to the value of the land for husbandry. If the observations are made further inland, among the mountains, then the increase of elevation must be taken into account. The winter here brings snow, and the summer is shorter than it is near the sea level. Hence the length of the growing season is diminished, but while it continues growth is extremely vigorous, especially in the month of June. The abundant supply of water, wood, and the bracing mountain air, compensate for a frequently inclement winter, the difficulty of transportation, and a short summer season.
The founders of the early mission establishments in this region seem to have had a clear appreciation of these facts, and their locations were wisely selected, so as to embrace the widest extent of cultivable land, and the best situations for farms are still found to be in their vicinity. These missions occupy the valleys of the main water-courses, generally at that point where the supply of water can be depended upon in all seasons. Their aqueducts, bringing water from
towards the sources of the streams or from local springs, were often of great length and magnitude. The one belonging to the San Diego mission, for instance, is a continuous wall of masonry for the distance of nearly three miles. The upper portion of each valley was generally occupied by a branch dependency of the main mission, thus securing the entire control of the agricultural resources of the valley.
In regard to the eastern slope of the mountain but little additional need be said. In the immediate vicinity of the summit ridge arable land is found, but the more precipitous slope renders this too limited in extent to claim much attention. Desert valleys and pent up cañons succeed between this and the great plain. As far as all agricultural purposes are concerned this is truly a desert, though it is not, as is generally supposed, a mere waste of shifting sands, and destitute of every kind of vegetation.
We have already noticed that several shrubs are peculiar to this tract, which, if they serve no other purpose, at least afford relief to the eye.
The borders of “New River” being subject to frequent if not regular overflow, would seem to present some opportunities for the limited cultivation of maize, beans, pumpkins, and melons, such as is practiced by the Indians on the Colorado, and the existence of “gramma grass” on the higher adjoining ground would seem to indicate that quickly maturing cereals might be raised here.
The supply of water might, moreover, be rendered more constant and equable by the construction of artificial reservoirs and ditches. Still we must admit that any system of cultivation must be very precarious in a location where its success depends upon such variable causes.
The remarks respecting “New River” apply in a great measure to the Colorado. Here the cultivation is, of necessity, confined to those portions of the valley that are subject to overflow and the consequent deposition of fertilizing sediment. The higher adjoining lands, being without the reach of these influences, are, from their extreme aridity and the light porous nature of their soil, quite unfit for any cultivation.
All the Indian settlements upon the Colorado with which we are acquainted are located with reference to an overflowed portion of the river margin. Near the junction of the Gila with this river one Indian village occupies an old river bed, which, when the river is high, is completely covered by the stream. Another settlement is situated upon a low alluvial delta lying between the two rivers, and a third is built in a slough. These are also flooded at high water. The articles cultivated by these Indians are principally maize, beans, and pumpkins. No doubt that cotton, sugar, and many of the sub-tropical fruits would succeed here, but our present knowledge respecting the extent of arable soil, of the vicissitudes of the climate, and of the character of the different seasons, is too vague to warrant any but the merest conjecture in regard to its future agricultural importance.