PRINGSHEI.u's RESEARCHES ON CHLOROPHYLL. 99 



The only accurate method is to study the changes in the 

 ])huit-cells, aud, as a result of the investigations here re- 

 corded, the possibility of the destruction of chlorophyll 

 colouring matter by intense light in the living cells is 

 proved. Whether this goes on as a normal process is dis- 

 cussed at a later stage of this paper. 



Not only chlorophyll colouring matter, hut also yellow, 

 blue, and red, are in presence of oxygen destroyed within 

 the plant cells when exposed to intense light. Yet all 

 colouring matter found in plant-cells is not so acted on ; 

 different colouring matters under like conditions behave 

 differently. Observations are still wanted to show which 

 are destructible and which are indestructible, and to supply 

 the key to the relation between destructibility of these 

 colouring matters of the cells in light and their genetic 

 connection with chlorophyll colouring matter. As illustra- 

 tion : the red colouring matter of many resting spores of 

 ■AlgcB, especially oospores, is not destructible, or only with 

 extreme difficulty, by exposure to intense light. On the 

 other hand, the steel-blue colouring matter of the Phyco- 

 chromaccce (Oscillariecs, Nostocacece, &c), the brown oi Dia- 

 tomacecB, Phieosporece, and Fucacecs, and the ledi oi Flor idea, 

 in all their modifications, are, it ap[)ears, as easily de- 

 stroyed in intense light as the chlorophyll colouring matter 

 of green plants. 



Colouring matter of flowers seems to behave differently. 

 The yellow-red colouring matter of the ligulate flowers of 

 Calendula is with ease completely destroyed in intense 

 light, whilst that of Narcissus poetictis, in the same cir- 

 cumstances, remains unchanged. The blue cell-sap of 

 Tradescantia virginica loses its colouring matter easily 

 (fig. 27), whilst other blue flowers are decolorised with diffi- 

 culty, or not at all (see. Section vii, Experiment 48). 



Leipzi£r, ]859; 'Flora,' 1862, p. 219; 'Handbuch der Experimen'al- 

 pliysiologie,' 1865, p. 15. 



Askeiiasy, '■ Zur Kenntniss des Chloroplijlls," ' But. Zeit.,' 1867, p. 

 228 ; and " Ueber Zersloruno^ des Chlorophylls lebeuder Pflanzen durch 

 Licht,' ' Bot. Zeit.,' J 875, p. 457. 



Kraus, "Ueber wiiiterliche Verfarbung immergriiner Gewachse," 'Bot. 

 Zeit.,' 1872, p. 109. 



Batalin, " Ueber Zerstorung des Chlorophylls in lebenden Organeu," 

 'Bot. Zeit.,' 1874, p. 433. 



Wiesuer, " Ueber die Beziehung des Licbtes zum Chlorophyll," ' Sitz- 

 Tingsber. d. Wien. Akad.,' 1874; and 'Die natiirlichen Einrichtungen zuni 

 Scliutz des Chlor.jphyils,' Wien, 1876. 



Haberlandt, "Ueber die Wiiitertarbimg ausdaueruder Blatter," ' Sitz- 

 uiiffsber. der Wieu Akad.,' 1876. 



BoUm, '' Ueber Verlarbuiis^griiner Blatter im iutensiven Licht," ' Landw. 

 Vers. Stalionen,' 1877, p. 463. 



