66 



PHYSIOLOGY. 



The leaves arc made transparent by the chloral hydrate so that 

 the starch reaction from the iodine is easil}' detected. 



The followini:; is a convenient and safe metliod of extract- 

 ing chlorophyll from leaves. Fill a large jian, preferably a 

 dishpan, half full of hot water. This ma\' be kept hot b)' a 

 small flame. ( )n the water iloat an e\'a])orating dish parti}' 

 •filled with alcohol. The leaves should be first immersed in 

 the hot water for several minutes, then jjlaced in the alcohol, 

 which will ciuickly remove the chlorophyll. Now immerse the 

 leaves in the iodine solution. 



138. Green parts of plants form starch when exposed to 

 light. — Thus we find that in the case of all the green pilants we 

 have examined, starch is present in the green cells of those which 



FiK. 68. Fifr. 6q. 



Leaf of cnk-us slmwinj^ ^reeii and white .Similar leaf ireate.l with iudine, the stareh 

 areas, Ijefiire treatment with iodine. reaetiMii iniU- shMwinj.;: w-here the leaf 



was ^Teeii. 



have been standing for some time in (he sunlight where the proc- 

 ess of the absf)rj)tion of CU. and the gi\"ing off of oxvgen can 

 go on, and that in the case of plants grown in the dark, or in 



