52 CHLOROPHYLL. [CH. II 



fluorescent 1 . To observe this point compare it with 

 unaltered chlorophyll extract ; fluorescence is most easily 

 visible with a strong solution in a narrow test-tube. 



(60) Stability of the copper compound 2 . 



Fill two test-tubes A, B, with the copper compound 

 and two others C, D, with unaltered leaf-extract : place A 

 and G in sunlight, B and D in the dark. After some 

 hours note by comparison with B and D that the copper 

 compound is not destroyed while G is affected. 



(61) Spectroscopic examination. 



To see the characteristic chlorophyll band / in the 

 red, a small direct-vision spectroscope may be used : the 

 solution may be in a test-tube, and ordinary daylight will 

 suffice. In Detmer's Praktikum, p. 17, a convenient 

 holder for test-tubes is figured and described. For the 

 other bands direct sunlight is needed, the solution, which 

 must be a weak one, should be placed in a parallel-sided 

 vessel, and a more elaborate spectroscope should be used. 



(61 A) Part of the red rays not absorbed. 



If a thick layer (say 5 or 6 cm.) of strong leaf-extract 

 is placed between the observer and a source of light it 

 appears red instead of green. This is an interesting 

 demonstration of the fact that the part of the spectrum 

 on the infra-red side of the BG band is that which is 

 least absorbed by a chlorophyll solution. 



(62) Other pigments (Anthocyan). 



The red varieties of Ricinus and Amaranthus may be 



1 Tschirch, Deut. Bot. Ges. Ed. v. 1887, p. 135. 

 8 See Schunck, Annals of Botany, in. p. 94. 



