23 



NEW YOKK HAY MARKET. 



The following is a comparison of the prices of hay and straw in the 

 New York market for the past three years 



THE NORTH AMERICAN DESERT FLORA BETWEEN 32° AND 

 42°, NORTH LATITUDE. 



The following- paper was read at the meeting (1870) of the British 

 Association at Liverpool, England, by C. C. Parry, j\L D., the botanist 

 of this Department: 



The desert tracts of North America, as at present defined by our recent geographical 

 knowledge, comprise those interior basins of greater or less extent shut in by mountain 

 ranges from (the influence of the moist oceanic currents. These well-marked districts, 

 while presenting certain diversities of soil corresponding to particular geological con- 

 ditions, everywhere characterized by an arid climate, irregular and scanty rainy 

 seasons, and wide extremes of heat and cold, both diurnal and annual. The permanent 

 ■water-conrses of this regicm, having their distant sources in snow-clad summits, traverse 

 a succession of basins, presenting occasional alluvial belts bounded by elevated and 

 abrupt table-land, which latter is mainly composed of beds of coarse gravel or drifting 

 sand. The intervening ridges forming the basin rims are cut through by those deep 

 chasms known as canons. 



The local drainage, not connected with the main valleys, terminates rather in salt 

 lakes or saline flats, the intense evaporation being sufficient to carry off the superficial 

 supply of water, leaving their soluble mineral contents to be concentrated in the lower 

 depressions. The intervening rocky ridges and isolated mountain peaks, when not of 

 sufficient elevation to act as condensers of the upper currents of the atmosphere, exhibit 

 the same characters of arid vegetation, though comprising a larger proportion of 

 shrubbery and dwarf-tree growth. 



In attempting an enumeration of North American desert xdants, my aim has been not 

 so much couipleteness of detail as to exhibit the main features of desert vegetation, as 

 here brought to view, and to afford the means of comparison with corresponding dis- 

 tricts in other portions of the earth. One of the most striking features of the desert 

 flora may be noted in the very marked distinction between the annual and perennial 

 vegetation. Thus, the annual desert plants, whose period of growth is strictly confined 

 to a short and uncertain period of spring or fall rains, require for their continued preser- 

 vation a safe deposit for their usually minute seeds during the prolonged dry season. 

 This condition is, in great measure, supplied by the porous sandy and gravelly soil, or 

 rock crevices, into which they fall and are safely buried, not only out of the reach of 

 climatic influences, but also safe from destruction by animals. Their growth is neces- 

 sarily rapid and evanescent, and no sooner do warm rains moisten the ground than 

 they spring forth from their hiding places and clothe the barren soil with their scanty 

 verdure, rapidly flower and mature their seeds, which are again deposited in the earth, 

 while their slight evanescent forms dry up and are blown away, hardly leaving any 

 visible trace of their existence. These characteristics are plainly exhibited in ordinary 

 herbarium specimens, and are further exemplified in the specific name of "exile," so 

 often very appropriately applied. On the other hand, the perennial desert plants either 

 store up a large amount of surplus nourishment in their thick, tuberous, or tap roots; 

 or, in the case of trees and shrubs, present exposed stems and foliage of the most scant 

 and starved character. Spine-clad branches and green-barked stems are, in many 

 instances, made to supply the office of leaves, or where these latter are present, they 

 are often thickly coated'with resinous varnish, or clothed with tomeutose hairs or 

 scales, serving, in either case, to check evaporation, and thus limit the usual processes 

 of growth. The preservation of species in perennial plants being less dependent than 

 in annuals on the production of seeds, these are generally scanty, often mature late, and 



