in 'which Cotton unites with Colouring Matter. 24>5 



search. But I shall resume these observations with a more 

 perfect instrument, which I hope soon to possess. 



We have moreover the powerful analogy of the arrange- 

 ment of colouring matter in plants in support of this view of 

 the case. " Cellular tissue," says Dr. Lindley in his Introduc- 

 tion to Botany, "generally consists of little bladders or vesi- 

 cles of various figures adhering together in masses. It is trans- 

 parent, and in most cases colourless ; when it appears other- 

 wise its colour is caused by matter contained within it." 



" The bladders of cellular tissue are destitute of all perfora- 

 tions, so far as we can see, although, as they have the power 

 of filtering liquids with rapidity, it is certain that they must 

 abound in invisible pores." " The brilliant colours of vege- 

 table matters, the white, blue, yellow^ scarlet, and other hues 

 of the corolla, and the green of the bark and leaves, is not 

 owing to any difference in the colour of the cells, but to the 

 colouring matter of different kinds which they contain. In 

 the stem of the garden balsam a single cell is frequently red 

 in the midst of others which are colourless. Examine the red 

 bladder, and you will find it filled with a colouring matter of 

 which the rest are destitute. The bright satiny appearance 

 of many richly-coloured flowers depends upon the colourless 

 quality of the tissue. Thus in Thysanotus fascicularis, the 

 flowers of which are of a deep brilliant violet, with a remark- 

 ably satiny lustre, that appearance will be found to arise from 

 each particular cell containing a single drop of coloured fluid, 

 which gleams through the white shining membrane of the 

 tissue and produces the flickering lustre that is perceived." 

 Cotton is itself cellular tissue, and the ligneous basis of all the 

 forms of these vessels has the same chemical constitution. 



I have alluded to another class of processes in dyeing in 

 which the action much more resembles chemical affinity. I 

 mean that in which pure cotton by mere immersion in different 

 liquids withdraws a variety of substances from their solution. 

 The " indigo vat" is a transparent solution, of a brownish yel- 

 low colour, consisting of deoxidized indigo combined with lime, 

 and containing seldom more than y^th of its weight of co- 

 louring matter. By merely dipping cotton in this liquid the 

 indigo attaches itself to it in the yellow state, in quantity pro- 

 portioned within certain limits to the length of the immer- 

 sion ; and all that is necessary then to render it blue is to ex- 

 pose it to the air. Here an inactive spongy substance exer- 

 cises a power which overcomes chemical affinity, but the mix- 

 ture, which is formed of cotton and indigo, possesses none of 

 the characters of a chemical compound. We can only recog- 

 nise in this action the same force, whatever that may be, which 



