BOTANY OF THE 40TH PARALLEL. 183 



Mr. Watson raises the question whether — considering the 

 amount of low shrubby and perennial vegetation which inhabits 

 the plains and thrives without irrigation — these plants them- 

 selves, or some more serviceable substitutes equally adapted to 

 the climatic conditions, may not be turned to some profitable 

 account under the necessities of a future population ; and 

 whether, in time to come, some forms of orchard, vineyard, or 

 tree-culture may not possibly be made to thrive in that region. 

 He finds that the present plants on the whole are not lacking 

 in expansion of foliage or succulence, at least that the more 

 prevalent plants had an average of from 55 to 80 per cent. 

 of foliage or working surface ; and a series of rough but seem- 

 ingly well-devised experiments demonstrated that they give 

 off by evaporation daily an amount equal to three eighths of 

 the weight of their available material. Dry as the soil appears 

 to be, it is this, and not the atmosphere, that must furnish the 

 supply to make good this loss. Yet water is rarely to be had 

 under a depth of 100 to 300 feet, often not even at that depth. 

 The porous soil must allow of the free upward diffusion of 

 moisture, also of deep penetration of the roots from above. 



An excellent map is given, exhibiting the district from 

 above the 42d parallel to below the 39th, on which the routes 

 of the three several years are traced in colored lines, and the 

 mountain ranges with the general configuration of the surface 

 represented. We will endeavor hereafter to review the sys- 

 tematic part of this work. 



(Second Notice.) — Under the modest name of a catalogue 

 of the known plants of Nevada and Utah, Mr. Watson has 

 given us a treatise, not to say a Flora, of a wide stretch of 

 country between the Sierra Nevada and the Rocky Mountains, 

 which is invaluable to the botanist studying the plants of that 

 region in herbaria, and still more to explorers on the ground, 

 — of which we hope there may be many. For not only are 

 new or revised species described, but all species not contained 

 in the common eastern manuals, etc., which every collector is 

 supposed to possess ; the characters of western genera are 

 appended in foot-notes, and synopses of recently elaborated 

 genera — some of them reprints or translations of scattered 



