l8 PHYSIOLOGY OF NUTRITION 



known. Chlorophyllogen is a very unstable substance, and its absorption spec- 

 trum shows a great similarity, in the red region, to that of chlorophyll. 

 Attempts to isolate it result in an artificial transformation-product, the proto- 

 chlorophyll of Monteverde. 1 Like chlorophyll, protochlorophyll is a deep green 

 pigment, which is fluorescent, appearing red by reflected light. The spectrum 

 shows four absorption bands. The absorption spectra of alcoholic solutions of 

 protochlorophyll on the one hand, and of alcoholic chlorophyll on the other, 

 are different in that the absorption band between B and C in the second is absent 

 in the first, and the one between C and D in the first appears slightly displaced 

 toward the left in the second; the other bands practically agree. Although 

 protochlorophyll is a transformation-product, it is still of interest, in so far as 

 its existence indicates the presence of a mother-substance for chlorophyll; 

 protochlorophyll itself cannot change into chlorophyll. Protochlorophyll 

 arises independently of light, from chlorophyllogen. As to its presence in 

 living cells, it is normally found in large quantities in the inner seed-coats of 

 the Cucurbitaceae, especially inLuffa. 



A rapid transformation of chlorophyllogen into chlorophyll occurs in living 

 plant cells under the influence of light. This process can also be observed in 

 plants that have been killed. According to Liro, if etiolated leaves are care- 

 fully killed so that at least some of the chlorophyllogen remains, and if they are 

 then exposed to light, some formation of chlorophyll can still be observed. For 

 the transformation of chlorophyllogen into chlorophyll, Liro and Isachenko 2 

 have shown that neither oxygen, favorable temperature conditions, nor even 

 the presence of carbohydrates are necessary, but since greening is possible only 

 with these conditions they are evidently necessary for the formation of chloro- 

 phyllogen, or of the chromogen that gives rise to it. Chlorophyll may be formed 

 from chlorophyllogen in the absence of light, as is exemplified by plants that 

 turn green in darkness; in such cases the influence of chemical agents must 

 replace the action of light. 3 



Such are the chief results of the researches thus far carried out upon chloro- 

 phyll and its formation. As to the role it plays in the chemical decomposition 

 of carbonic acid and the formation of the first products of photosynthesis 

 almost nothing is known. Schryver 4 suggests that the formaldehyde arising 

 in the decomposition of carbon dioxide and water enters into combination with 

 the chlorophyll. 



» Monteverde, 1894. [See Note, 1, p. 9.] Monteverde, N. A., Der Einfluss des Lichts auf die Gesch- 

 windingkeit deT Chlorophyllbildung in Blattern etiolirter Pflanzen. Trav. Soc. Imp. Nat. St.-P6tersbourg 

 27' ': 131-142 [Russian], 143-145 [German abstract]. 1896. Idem, Das Protochlorophyll und Chlorophyll. 

 [Title and abstract in German, article in Russian.] Bull. Jard. Imp. Bot. St.-Petersbourg 2: 179-182. 

 [Abstract, p. 181-182.] 1902. Idem, Ueber das Absorptionsspectrum des Protochlorophylls. I. [Title 

 and abstract in German, article in Russian.] Ibid. 7: 37-42 [Abstract, p. 42], 47-58. [Abstract, p. 5S~58]. 

 1907. 



' Issatchenko, B., Sur les conditions de la formation de la chlorophylle. [Title and abstract in 

 French, article in Russian.] Bull. Jard. Imp. Bot. St.-Petersbourg 6: 20-28 [Abstract, p. 27-28]. 1906. 

 Idem, same title. Ibid. 7: 59-64 [Abstract, p. 64]. 1907. Idem, same title. Ibid. 9: 106-120 [Ab- 

 stract, p. 119-120]. 1909. 



3 Monteverde and Liubimenko, 1911. [See note 6, p. 17.] 



4 Schryver, S. B., Photochemical formation of formaldehyde in green plants. Chem. news 101 : 64. 

 19TO. 



