1917] MARKLE—ROOT SYSTEMS 179 
months prevent the growth of the winter annuals so characteristic 
of the Tucson region. 
TABLE I 
RAINFALL 
Jan. | Feb. | Mar.| April) May | June | July | Aug. Sent, Oct. | Nov. | Dec. | Total 
Tucson. ... 79|0.90/0.77/0.27\0.14/0. 26|2.46|2.66|1.16/0.64/0.81|1.00|/11.17 
Albuquerque, 
average... . 0.4810. 33/0. 22/0. 26/0.69/0.35|1.43|/1-07|1.70|0.77/0.46) 31 | 7-44 
Albuquerque, 
TORRE 0.68]0. 56/0. 51/2.05/0.00|0:00) eS Ares ae ee 
TEMPERATURE 
| x803 | s808 | 180s | 1896 | 807 | 2808 | 3800 | 1000 root | 902 
minimum II Ol 3) M41. 3 ° ee 4{| 42 
Absolute maximum 98 | 95 | 95] 100 | 95 | 104 | 104 | I0r | 99 | 100 
EVAPORATION FROM A FREE WATER SURFACE 
a caienl a pie ae 
fapestl 73] 1.49 - 
The data for Tucson are rc i pila ree wid “MacDoven 
= 2 
soon found that such data are of little value, since on account of 
the fact that the soil is composed of stream-borne material, it is. 
subject to extreme local variations, even within the habitat of a 
‘single plant, as is shown in th iptions of the habitats of most _ 
-h nitions | 
_ of the plants given in this paper. "Samples of soil from different — ee 
| levels in the habitat of forces canescens showed the ane : rs oe 
