PHOTOSYNTHESIS 



83 



the whole clamped in a frame which carries in front of the slit two spring 

 clips arranged to hold a small flask, or vial, of chlorophyl solution, which 

 of course can be made of greater or lesser density. It may be set in front of 

 a light, when the lands may be studied and mapped at leisure, or, the base 

 being unscrewed from the handle, it may be passed around the class for 

 demonstration, each student directing it towards some selected source of 

 light. A microspectroscope, for use with the microscope, as described by 

 Detmer, 23, may also be used, but is very expensive, and for our present pur- 

 pose has no advantage over the above instruments/ "t Different thicknesses 

 of solution may most effectively be secured by use of triangular troughs sold 



Fig. 15. — An efficient arrangement or the spectroscope for the study 

 of chlorophyl; upper section as seen from above, lower from the 

 side, Xi. 



The dotted lines show the path of light, reflected in part by mirrors, from a single incan- 

 descent lamp. The chlorophyl is in the flat (Soyka) flask. 



by dealers in chemicals, though the cement of some of these is attacked by 

 alcohol. Very good and well-colored pictures of chlorophyl spectra are in 

 the Frank and Tschirch diagrams (page 23), Plates XV, XVI. 



Demonstration. The chlorophyl spectrum may be shown to a class, 

 though not to all simultaneously, by the hand instrument above described 

 and figured (Fig. 16). It should be possible to project the spectrum finely 

 upon a screen with a projecting spectroscope. 



