HOW THK I'LANT lJVT.fi. 



125 



plnrnl is stomata or ntomntfB. Fi>r. 'AS bLowb n frnpmont of leaf 

 iit cross- ^'ot ion, a boinj; a Ktoma opening out on the lowt-r sur- 

 face. Looking; down upon the 

 peeled-ofT epidt-miis of the lower 

 surface, stonmta are seen at Fip. 39. 

 I88b. Cut off a leafy branch of 

 any herh, insert the stem through 

 a perforated cork into a bottle <jf 

 water, and then place the whole 

 under a bell -glass. Note how soon 

 the water vapor thrown off condenses 

 upon the plass. Compare Fig. 10, 

 page 58. 

 lnHc. The rate of tran W 

 spiration from a single leaf Vv 

 may be accurately obser^'ed 

 as follows : A large U- 

 shaped glass tube is filled 

 with water, and into one end 

 of this tube is inserted a 

 perforated cork bearing a 

 small glass tube or capillary 

 arm, bent at right angles. 

 In the other end of the U- 

 tube is fitted a cork, through 

 the perforation in which is 

 inserted the leaf-stalk, with the stem reaching 

 the water, as shown in Fig. 40. When this last 

 ■'ork is forced in, water will fill the capillary arm: 

 and the reccsaioD of the water in this arm to 

 supply that transpired shows the rate of tran- 

 spiration. Wax or parafUn sboold b« usmI to S4^al 

 around tho perforations. 



189rt. lioot-pressure or sap-pressure, may he 



made evident roughlv by a verv simple experiment. 



" • . ' J , Fl*. ST. How tb« 



An inch or so above ground, cut off a stem of some ^^ adhnrwi to 



artirely-growing herbaceous plant, as the sun- th* yoons tool. 



Kig. 34. The root-liaim 

 «• M^n un ft dark, 

 damp cloth. 



