THE CHLOROPLAST 89 



lengths. The instrument, with quartz components and a xenon arc 

 Hght source, can l)e used over the wave-length range 200 to 990 

 m^u, at a low magnification for specimen areas of 16;Lt- to 2|U,-, at an 

 entering half -band width of 2.6 m/^. In Fig. 2 are shown the ab- 

 sorption spectra obtained with this instrument for the chloroplasts 



MICRONS ACROSS CHLOROPLAST 



Fig. 4. Absorption across a single chloroplast at 0.5/x intervals as measured 

 at 675 m/j. relative to 550 myu, with the microspectrophotometer, indicating the 

 distribution of chlorophyll in the chloroplast. 



in two different euglenas. The magnification was 250X; an area of 

 8|U- is represented. These spectra begin to show fine structure. The 

 major absorption peaks are near 675 and 435 m/u, with other peaks 

 at 480, 590, and 625 yu/jl. Since these are in vivo spectra, some shifts 

 are to be anticipated from the spectrum of the pigments dissolved 

 in organic solvents. These spectra (Fig. 2) closely approximate 



