194 Alfred J. Ewart : 



of carotin continued at a greal^er rate than it was used in the for- 

 mation of chlorophyll. 



To test this, two batches of wheat seedlings were grown in dark- 

 ness, until approaching partial starvation. One batch was then ex- 

 posed to full sunlight for one day. Equal quantities were then dipped 

 in boiling water, the surplus Avater squeezed out, and the leaves 

 twice digested with cold absolute alcohol on two successive days. 

 The fully etiolated leaves were still deep yellow, and with hot alcohol 

 gave a strong, nearly pure solution of carotin. Those which had 

 been exposed to light were nearly colourless, and gave a pale yellow 

 solution with hot alcohol, containing only a small amount of 

 carotin. 



Kohl is, however, correct in stating that carotin is the chief pig- 

 ment in etiolated seedlings. Complete extractions with etiolated 

 wheat seedlings yielded from 8 to 10 parts of carotin to one of 

 xanthophyll, the percentage may of course vary Avith other seed- 

 lings, and after prolonged etiolation it appears to decrease. 



If colourless precursors of chlorophyll exist, they should have a 

 high magnesium content, and should be capable of separate extrac- 

 tion. An area of ten square feet of closely planted AA'heat Avas kept 

 in darkness until the seedlings were six inches high. The yelloAv 

 leaves Avere cut at once and dropped into boiling Avater, and after 

 squeezing out all excess of Avater, tAvice digested in cold alcohol for 

 periods of a day, all liquid being squeezed out in a strong press after 

 each extraction. The nearly colourless material AA-as then digested in 

 boiling absolute alcohol for five hours. Tlie solution Avas filtered 

 hot, petrol ether added while still Avarm. and sufficient Avater to 

 bring about separation. After standing for a day the pale yellow 

 petrol ether extract Avas evaporated to dryness, and the residue 

 dissolved in a minimum of hot alcohol. In this solution, after 

 standing for one day, a bulky white crystalline solid separates out 

 Avhich appears to contain alcohol of crystallization. After filtering 

 and Avashing with a little absolute alcohol a pale broAvnish Avhite 

 solid Avas obtained. This gave off alcohol AA'hen heated, and after 

 incinerating Avith a drop of nitric acid yeilded 1.5% of ash as mag- 

 nesium oxide. 



The original precipitate, hoAvever, appears to consist of two solids 

 — (a) a Avhite Avax less 8oluble in cold alcohol than carotin, but readily 

 soluble in hot alcohol; and (b) a broAvner Avax, Avhioh is still less 

 soluble in alcohol, than the preceding, and can be separated from 

 it by Avashing Avith small amounts of warm alcohol. This less 

 soluble broAvner Avax yielded in one experiment 6.2% of ash as mag- 



