2 inven mcet, 16 by 
A. Reduction of transpiration. 
Ist, reduction in size of leaves, surface. 
2nd, hairy coverings. 
ard, stomates deeply sunk. 
Ath, cuticle thickened. 
5th, leaves dispensed with. 
6th, stems shorter, with thick cuticle and 
and often hairy or waxy coverings. 
B. Provision for water storage. 
Thick, fleshy trunks or leaves, and roots. 
C. Increased surface for root absorption. 
Great length and branching. 
Extend often to great depths. 
Thorny or spiny character of desert vegetation. 
3. The Sonora-Nevada Desert. 
Location, valleys of great basin ranges. 
Note Desert Botanical Laboratory. 
Types of conditions are 4 in the region. 
i @ases: 
a. Along streams. 
b. By springs. 
c. By basins where there is ground water, hydros- 
tatic water. 
2. Higher altitude on mountain sides, coniferous forest, 
heavy snows, water doled out through a long period. 
Elevated areas adjoining desert proper. 
Receives some moisture from mountains, cactus, 
yuccas, greasewoods, etc. 
A. Desert areaiproper: 
(1) Two distinct floras. 
Tst, annual or rainy season flora. 
2nd, perennial or true desert fora: 
(2) Rainy season depends on storm water, De- 
cember-March. 
a. Water held in capillarity for several 
feet 
b. Vegetation begins February and March. 
c. Evaporation from soil and transpiration. 
ioe) 
42 
