samina horlensis. 405 



of Grew, Mirbel, and others* The wounded surface of the 

 stem, as well as that of the detached strip, was examined with 

 and without immersion in water ; still, not a tint of colour 

 was afforded; nor could any be obtained on inspecting a 

 small slice cut horizontally across the stem. 



2d, The plant with the red stem, which had grown in the 

 coloured infusion, was next investigated ; but it was void of 

 tint in any part of its organisation, except on the epidermis. 

 Hereon, indeed, a most interesting spectacle was exhibited ; 

 for the natural colouring matter which afforded the red tint to 

 the skin, was found to be deposited in the most fanciful and 

 beautiful forms imaginable. As a splendid object, when 

 viewed under every different degree of light, from complete 

 shade to the glare of full and condensed sunshine, I cannot 

 conceive one that can surpass it ; and I earnestly recommend 

 your readers who possess, or can command the use of, good 

 microscopes, to devote strict attention to a careful observance 

 of so wonderful a combination of colours. As far as my testi- 

 mony may go, it can be compared only to a tissue, or net- 

 work, composed of threads of brilliant crimson foil, fancifully 

 and irregularly spread over a surface of glittering and greenish 

 silver. 



To return from this digression to the subject of my com- 

 munication : I have already observed that the examination 

 detected no traces of the colouring matter of the logwood in 

 an)' part of the subjects investigated ; consequently, no light 

 has been thrown, by these experiments, upon the mystery which 

 involves the enquiry concerning the proper channels of the 

 two saps. Sir H. Davy observes, in his sixth agricultural 

 lecture [Lectures on Agricultural Chemistry ', edit. 1827, p. 243.), 

 that " the pores in the fibres of the roots of plants are so 

 small, that it is with difficulty they can be discovered by the 

 microscope ; it is not, therefore, probable, that substances can 

 pass into them from the soil. I tried an experiment on this 

 subject. Some impalpable powdered charcoal, procured by 

 washing gunpowder, and dissipating the sulphur by heat, was 

 placed in a phial containing pure water, in which a plant of 

 peppermint was growing ; the roots of the plant were pretty 

 generally in contact with the charcoal. The experiment was 

 made in the beginning of May, 1805; the growth of the plant 

 was very vigorous during a fortnight, when it was taken out 

 of the phial : the roots were cut through in different parts, 

 but no carbonaceous matter could be discovered in them, nor 

 were the smallest fibrils blackened by charcoal, though this 

 must have been the case had the charcoal been absorbed in a 



solid form." noqz9Ti®n rhidv/ 



dd 3 



