52 



but we already know from other experiments by Alex. v. 

 Humboldt, DeCandolle, and others, what a small quantity 

 of light plants absolutely require, and that the formation of 

 vegetable colours does not proceed from the direct influence 

 of light. 



The plant, which had been grown under ground, exhibited 

 a change of the yellow colouring substance, namely, of the sap 

 globules coloured by chlorophylle into the yellow colour, which 

 was dissolved in the cellular sap ; M. Decaisne has even ob- 

 served this change of the chlorophylle at various periods, and 

 has thus been enabled to follow it up more accurately ; he has 

 also elucidated these observations by several highly instructive 

 coloured illustrations. I have observed this change of the 

 chlorophylle into a yellow colouring substance, soluble in the 

 cellular sap, in young plants of Vicia Faba, which had been 

 grown immediately on their appearance in a dark situation ; 

 at the same time cells with red coloured sap also occurred. 

 All these colours disappear if the plants are exposed for some 

 time to light. 



We have finally to notice M. Mohl's * observations on the 

 occurrence of chlorophylle in the green coloured cellular sap 

 globules, a subject which is for the first time specially men- 

 tioned in this memoir. About the same time a separate section 

 of my Vegetable Physiology (i. p. 200) was devoted to the same 

 subject : "Occurrence of coloured cellular-sap globules." The 

 results of these observations are as follows : M. Mohl and I 

 agree that the chlorophyUe appears in the cells of plants partly 

 in an amorphous and partly in a granular form. This and 

 other facts respecting this questionable subject were pub- 

 lished by me some years agof to refute Treviranus' view, 

 that the cellular sap is never of a green colour, which is now 

 confirmed by M. Mohl. The occurrence of amorphous chlo- 

 rophylle in the cells of Conferva is noticed by Mohl, and a 

 number of perfect plants are enumerated in which amorphous 

 chlorophylle occurs together with granular in the cells. In 

 Phanerogamae, observes M. Mohl, amorphous chlorophylle 

 is generally met along with granular chlorophylle in the 



* Untersuchungen liber die anatomischen Verhaltnisse des Chlorophyll's. 

 An Inaugural Dissertation. May 1837, Tubingen. 



t Year's Report for 1 835. Wiegmann's Archiv., part III. 1836, p. 90. 



