

RAINFALL IN DEATH VALLEY. 33 



(d) Annuals — Continued. 



Oxystylu lutea. Piptocalyx circumscissm. 



Pectocarya linearis. Plantagopatagonicagnaphaloidcs. 



Perityh emoryi inula. Pterostegia drymarioides. 



Pkacelia crenulata. Salvia columbaria'. 



Phacelia fremontii. Sty Iodine micropoidet. 



Pkacelia pachyphylla. Sisymbrium canescens. 



CHARACTERISTICS AND ADAPTATIONS OF THE DESERT FLORA. 



SOURCE AND DISTRIBUTION OF MOISTURE. 



The amount of rainfall in Death Valley has never been recorded for 

 the entire year. The observations of the Weather liureau for the five 

 months, May to September, 1891, show a total amount during that time 

 of 1.4 inches, 1 but since the rainfall for the whole desert region is known 

 to be distributed nonunifonnly through the year, this record undoubt- 

 edly docs not represent five-twelfths of the total amount. An average 

 of ten Weather Bureau stations 2 in the adjacent desert region probably 

 represents more nearly the actual yearly rain fall in Death Valley. This 

 average is 5.155 incites— in round numbers. 5 inches. The utter in- 

 adequacy of this amount to support any ordinary vegetation may be 

 comprehended by comparing it with the average yearly rainfa 1 at 

 Dodge City, Kansas. For the years 1874 to 1883 the mean annual rain- 

 fall at this point was 20.09 inches. 3 In the vicinity of this place wheat, 

 sorghum, and alfalfa cannot be grown without irrigation, under the old 

 methods of cultivation, save in an exceptionally favorable season. The 

 mean annual rainfall at Washington, D. C, for the years 1872 to 1883 

 was 43.27 inches. 4 



The distribution of rainfall through the year is especially important. 

 The average of the mean monthly rainfall at the ten stations noted 

 above is as follows : 



Inches. 



January 638 



February 609 



March _.. 642 



April ii;r, 



May - 318 



June 035 



Inches. 



•Tnly 218 



August 300 



September 141 



October 184 



November 278 



Decern ber l. 627 



A glance at this record shows that the rainy months are December, 

 January, February, and March. The first two of these months are the 

 coldest of the year, so that the rain which falls during that time seldom 

 shows any immediate marked effect on the vegetation ; but the increas- 

 ing temperature of February and March, accompanied by a good rain- 



. l Bulletin No. 1, Weather Bureau, p. 25 (18!)2). 



8 Barstow, Bishop Creek, Camp Cady, Camp Independence, Daggett, Fenner, Keeler, 

 and Needles, in California; El Dorado Canon, in Nevada; and Yuma, in Arizona. 



3 Ann. Rep. Chief Signal Officer of the Army for 1881, p. 301. 



<Ibid., p. 303. 



13095— So. 1 3 



