806 FLUORESCENCE OF PIGMENTS IN VIVO CHAP. 24 



saw it— Tswett (1911), Lehmann (1914), Wilschke (1914) and Gicklhorn 

 (1914) — that they gave enthusiastic descriptions of this phenomenon. 

 More recently, green leaves, green and colored algae and diatoms have all 

 been studied under the fluorescence microscope, by Lloyd (1923, 1924), 

 Testi Dragone (1927), Klein and Linser (1930) and Metzner (1937). 



In the meantime, methods of macroscopic observation of plant fluores- 

 cence also have been improved, and Stokes' original results confirmed and 

 expanded. Notably Dhere and co-workers (see Dhere 1937, 1939) have 

 carried out numerous spectrophotographic investigations of plant fluores- 

 cence: Dhere and Fontaine (1931), Fontaine (1934) and Dhere and Raffy 

 (1935) studied brown, green and blue algae; Bachrach and Dhere (1931), 

 diatoms; and Dhere and Raffy (1935) and Dhere and Biermacher (1936), 

 green leaves. The investigations of Kautsky and co-workers (1932-1943), 

 McAlister and Myers (1940), Franck, French and Puck (1941), Shiau and 

 Franck (1947) and of the "Dutch group" (Wassink, Katz, Dorrestein et at. 

 (1939, 1942, 1945) dealt mainly with the alterations in the intensity of 

 fluorescence that accompany changes in the rate of photosynthesis. 



French and co-workers (1948, 1951) and Duysens (1951) initiated a 

 very promising spectrophotometric investigation of fluorescence, particularly 

 of red algae. 



1. Fluorescence Spectra of Plants 



If we leave aside the phycobilin-carrying algae, the spectroscopic pat- 

 tern of the fluorescence of living plants is very simple. In solutions, both 

 chlorophyll a and chlorophyll h have a two-band fluorescence spectrum in 

 the visible region (cf. Table 23.1). In the living cell, these bands are 

 shifted so far toward longer waves that only one band of chlorophyll a 

 and one of chlorophyll h remain within the visible spectrum. Thus, the 

 visible fluorescence spectrum of green leaves and green algae consists of 

 only two bands. 



Brown algae and diatoms contain no chlorophyll h; their fluorescence 

 spectrum therefore shows only one visible band. It was mentioned on 

 page 406 that Wilschke (1914) and Dhere and Fontaine (1931) observed 

 a second band in the fluorescence spectrum of heat-killed brown algae 

 and extracts from these organisms, and attributed it to a "chlorophyll 

 c" (chlorofucin) ; but no corresponding band was found by Dhere and 

 Raffy (1935) in the fluorescence spectra of living brown algae. Manning 

 and Strain (c/. page 614) concluded more recently that a chlorophyll c 

 actually exists in live diatoms; but they did not attempt to confirm this 

 by observation of the fluorescence band of this pigment in the spectrum of 

 the algae. 



The positions of the visible fluorescence bands of the two chlorophylls in 



