7032 Botanical. 



alpina, apparently unT^nown to all three writers, first figured by myself, ' Briiish 

 Ferns,' p. 79, and now found so abundantly by Mr. Backhouse and his friends, has 

 stronjif claims to be regarded as a distinct species. — Edward Newman.'] 



Presence of a potverful Colouring Mailer in Mercnrialis perennis. — The property of 

 the dog's mercury turning of a bluish or blackish green colour in drying, recorded by 

 Messrs. Hooker and Aruott at p. 367 of their ' British Flora,' has doubtless come 

 under the observation and perplexed many collectors of botanical specimens, but I 

 cannot ascertain that it has ever been attributed to the presence of a powerful, aud in 

 many respects peculiar, colouring matter. Many plants lose their colour in drying, 

 from the decomposition of the green pigment in its reaction with other products, as 

 tannin, &c. ; but the discoloration of the Mercurialis results from the production in 

 the process of drying of an extremely soluble bright blue colour, not the slightest 

 evidence of which occurs in the living plant, though of course, like many others, it pre- 

 exists in the plant in a colourless state. Gradual drying appears most favourable to 

 its development, as if the life of the plant is too suddenly destroyed by desiccation ; at 

 a high temperature little or none is produced. If the plant be allowed to gradually 

 wither and lose its moisture in the open air, the presence of the colouring matter is 

 made evident by (he green parts turning of an inky colour, and the blanched part of 

 the stem from underground of a rich metallic blue. The colour is most abundant in 

 the early spring, when the plant is about six inches high, and gradually disappears as 

 it attains its maturity in the autumn. The extreme solubility of the colour is easily 

 manifested by placing a little bit of the dried plant in cold water, which in the course 

 of a few minutes will be turned of a beautiful indigo-blue. When I first noticed it I 

 rejoiced in the hope that I had discovered a new source of indigo, but soon found its 

 properties in no way corresponded with that colour. Blue indigo is intensified in. 

 colour by sulphuric acid, and forms a straw-coloured compound with nitric acid. The 

 blue pigment of the Mercurialis, as far as I have been able to ascertain, is turned red 

 by all acids; indeed one of its principal characteristics is the extremely fugitive 

 character of the tint as at first developed, and its tendency to change into a reddish 

 purple. It differs from many vegetable colours, for example, litmus or red cabbage, 

 in the red, produced from its blue form by acids, not being reconverlible into blue 

 by an excess of alkali. A slight increase of temperature immediately converts the 

 blue into a reddish purple tint, which appears to be the only permanent form of the 

 colour. The blue colour also disappears on the solution standing for a few days, 

 probably the result of incipient fermentation. In the dry state, as it exists in the 

 plant, it appears to be more permanent, but I have not yet been able to dry from the 

 solution the blue form of the colour. As a liquid, whether red or blue, it invariably 

 evaporates to a rich reddish plum-coloured paste. I have been rather minute in the 

 description of its characteristics, in the hope that some one may investigate the subject 

 in a more practical form, and endeavour to utilize this product of one of our most 

 abundant plants. I have little expectation that the blue form of the pigment can be 

 made available by the dyer, but should think the permanent form, which is a fine rich 

 colour, would make an excellent dye. According to Dr. Lindley many of the natural 

 order to which the Mercurialis belongs have been made subject to the dyer's art. — 

 George Maw; Broselei/, March, 1860. 



