I'.ts 



PLANT STUDIES 



surface of the globular, cylindrical, or flattened stems (see 

 §:!r,). 



14(1. Hairy coverings. — A covering of bail's is an effective 

 sun screen, and it is very common to find plants of xeropbyte 

 regions character- 

 istically hairy (see 

 §35). ' The hairs 

 ;ire dead struc- 

 tures, and within 

 them there is air. 

 This causes them 

 to reflect the light, 

 and hence to ap- 

 peal' white or 

 lu'arlj' so. This 

 reflection of light 

 l(y tliehairsdimin- 

 ishes the amount 

 wliii'h reaches the 

 working region of 

 the plant (see Fig. 

 174). 



141. Body habit. 

 — Besides tlie va- 

 rious devices for 

 diiiiiuiKbing ex- 

 ])Osure or leaf sur- 

 face, and iience 

 1 II ss of water, 

 enumerated above, 

 the wliole habit of 

 tlie plant may em- 

 phasize the same ])urp(isc. In dry regions it is to lie observed 

 that, dwarf growths jn'cvail, so tliat the plant as a. whole 

 does not present such an exposure to tlie dry air as in 

 regions of greater moisture (see Fig. 175). Also the pros- 



Fl(^. K.5. T\V(i plants of accjiinium scourini; rush (Erpii- 

 ■■<(fillu)^ showing the effect of cliviroiiiiient ; the Ions, 

 iinbranched one having grown in normal megophyte 

 conditions ; the short, bnshy branching, more slender 

 form having grown on the dunes (scropliyte condi- 

 tions). — After CowLES. 



