PRODUCTION OF CHLOROPHYLL 225 



holds for the chlorophyll in the gynjecium of certain plants, 

 e.g. OrnitJiogaluni arabicuni. At any rate, in these cases, 

 the photosynthetic power is so small as to be masked by the 

 respiratory activity. 



Attention may here be drawn to the work of d'Arbamont,* 

 who considers that the plastids containing chlorophyll may be 

 divided into two classes, chloroplasts and pseudochloroplasts. 

 Of these the former include those bodies usually termed chloro- 

 plasts, and are characterized by the fact that they do not swell 

 in water, and do not, as a rule, stain when treated with acid 

 aniline blue. On the other hand, pseudochloroplasts swell in 

 water and do stain with aniline blue. In some cases plants 

 may contain pseudochloroplasts only.f 



With regard to the conditions necessary for the formation 

 of chlorophyll, light is the most important, but in addition a 

 certain degree of temperature, as well as the presence of certain 

 substances, such as iron and magnesium, are essential. There 

 is, however, some dispute regarding other factors. Palladin \ 

 states that chlorophyll formation is an oxidative process, and, 

 as a result of his experiments, finds that etiolated leaves on 

 exposure to daylight will not form chlorophyll unless a supply 

 of carbohydrate is available. If an etiolated leaf does not contain 

 carbohydrate, then greening will take place if the cut leaf be 

 placed in a solution of sugar. Almost any sugar will do, e.g. 

 sucrose, maltose, glucose, fructose, or raffinose ; success was 

 also obtained by the use of glycerine. The solution used must 

 be neither too weak nor too strong ; a strong solution of suc- 

 rose, for instance, will retard the chlorophyll formation because 

 it will depress oxidative processes. On the other hand, Issat- 

 chenko § finds that etiolated leaves of certain plants, e.g. those 

 of Vicia Faba, when detached from the plant and placed in 

 strong sugar solution, even 50 per cent, will form chlorophyll. 

 He considers that light is the all-important factor. D'Arba- 

 mont concludes that starch, and presumably also sugar, may, 

 or may not, be essential for the formation of chlorophyll. 



* D'Arbamont : " Ann. Sci. Nat. Bot.," 1909, 9, 197. 



t See Belzung: "Ann. Sci. Nat. Bot.," 1891, 13, 17; " Journ. Bot.," 1895, 

 g, 67, 102. 



X Palladin : " Bar. deut. bot. Gesells.," 1891, 9, 194, 229 ; 1902, 20, 224 ; 

 " Rev. Gen. Bot.," 1897, 9, 385. 



§ Issatchenko: " Bull. Jard. Imp. Bot., St. P^tersbourg," 1906, 6, 20. 

 15 



