8 4 



PLANT PHYSIOLOGY 



The student may also care to examine the spectrum of the 

 living leaf. This requires some special manipulation, as do 

 some other matters of correlated interest, which may be experi- 

 mentally studied by aid of the following suggestions: 



Suggested Experiments. The Spectrum of Chlorophyl in the Lea}. 

 Ordinarily this does not show well if the living leaf is held before the spectro- 



Fig. 1 6. — Spectroscope, student poem; X}. 



scope, because the air in the intercellular spaces refracts and scatters the rays; 

 but if the air be replaced by water (by immersing the leaf and exhausting the 

 air above it), the leaf becomes translucent, and its spectrum is plainer, though 

 the examination must be made at once, for the chlorophyl alters quickly; 

 or the leaf may be simply boiled in water, though this is less effective, since 

 it produces alterations in the bands. The leaf should be examined in water 

 either in a vial or between glass plates. 



