RELATION OF LEAF STRUCTURE TO PHYSICAL FACTORS 77 



Boebera papposa 



FOOTHILL MESA : light I ; available water 2-4% ; humidity 28- 

 77%; temperature 57-89 : staurophyll 300/1,; epidermis 25-40/4; 

 cuticle 3/4; chlorenchym (240/4) I close row prolate palisade cells 

 85 /4 next to upper epidermis, I row 60 /x next to lower epidermis ; 

 central oblobate cells. 



FOOTHILL THICKET: light 0.0125 ; available water 11% ; humidity 

 38-80% ; temperature 53-85 : diphotophyll 125/1,; epidermis 20/1; 

 cuticle thin; chlorenchym (85/4) I row prolate palisade cells 35 /*; 

 close globose sponge cells. 



Mesa ... C. 240 M P. 4-5 rows, 240 /* S. o staurophyll 



Thicket . C. 85/4 P. I row, 35 m S. 50^ diphotophyll 



I5SM 3-4 rows, 105^(43%) +50M 



Light i/So; water +(7-9%); humidity +(3-10%); tempera- 

 ture 4. 



Aster torreyi 



HALF GRAVEL: light i; available water 4.5-7.5%; humidity 30- 

 65%; temperature 5i-76: staurophyll 275/4; epidermis 20/4; 

 cuticle 10 /4 ; chlorenchym (225 /A) loose chains prolate cells 25-40 it. 



SPRUCE SHADE : light 0.03 ; available water 12-16% ; humidity 

 40-70%; temperature 48-72 : staurophyll 200/4; no other differ- 

 ence. 



The only variation from the type under shade conditions is a re- 

 duction in thickness of leaf. 



Light 1/33; water +8%; humidity +(5-10%); temperature 



-(3-4). 



Machaeranthera aspera 



GRAVEL: light i; available water 2.5-5.5%; humidity 30-65%; 

 temperature 55-76 : staurophyll 250 /4 ; epidermis 25 /* ; cuticle 5 /4 ; 

 chlorenchym (200/4) 4 close irregular rows prolate cells interrupted 

 by scattered globose and prolate water-storing cells 40/4. (Plate 

 VIII, fig. 8 a.) 



BROOK BANK THICKET: light o.on ; available water 18-20% ; hu- 

 midity 60-85%; temperature 47-6o, : diphotophyll 175/4; cuticle 

 thin; chlorenchym (125/4) i row prolate cells 40/1; lacunose oblate 

 sponge cells, and remains of lower prolate cells. (Plate VIII, 

 fig. 86.) 



