Mr. Hunt on the Influence of Light on Plants. 97 



the green colour of plants." It will be seen, on referring to 

 that communication (Phil. Mag., April 1840, p. 272), or to 

 my paper in the Report of the British Association for 1842, 

 on the same subject, that I have never yet dealt decidedly with 

 the question of the production of chlorophyl. It is true I have 

 stated that plants growing under green media were etiolated, 

 that under " the yellow solution they were less pale than those 

 which had grown in green light" that under red media they 

 grew " of an unhealthy colour" and " that under the blue fluid 

 there was a crop of cress of as bright a green as any which 

 grew in full light." From these results we might infer that 

 the so-called " chemical rays " were the most active in produ- 

 cing this green colouring matter, and I shall require a far 

 more extensive series of experiments than those of Dr. Gard- 

 ner before I am convinced that the mean luminous ray of the 

 spectrum is the most actively concerned in the production of 

 chlorophyl ; at the same time I have never pronounced any 

 decided opinion on this matter. 



On the question of the movements of plants towards the 

 light we are also at issue. I avoid any discussion on these 

 matters at present, as I am arranging a very extensive series 

 of experiments, which I hope to be enabled to complete pre- 

 viously to the next meeting of the British Association, before 

 which body I intend to bring my report. 



I hope in the mean time that both Professor Draper and 

 Dr. Gardner will pursue their investigations. I have previously 

 stated it as my opinion that the conditions of the solar rays 

 are different in the tropical and temperate climes ; and I am 

 convinced that similar experiments, tried in different parts of 

 the world, will lead to many very important facts connected 

 with the solar emanations. I have only to beg that I may not 

 be made answerable for more than my printed papers will 

 warrant. My experiments have been seen by scores of per- 

 sons during the periods of my residence at Devonport and at 

 Falmouth, and the results have been as I have stated. That 

 light retards germination the common experience of every one 

 proves, but I am willing to allow that results obtained as mine 

 have been, with coloured media (although carefully analysed), 

 are liable to many objections. I have devised methods by 

 which I shall repeat these researches with the prismatic rays 

 during the coming spring and summer. Soliciting your in- 

 sertion of this short correction of Dr. Gardner, 



I remain, dear Sir, 



Yours very obediently, 

 Falmouth, Jan. 9, 1844. Robert Hunt. 



Phil Mag. S. 3. Vol. 24. No. 157. Feb. 1844. H 



