102 Mb. Crum on ike Mcmner in which Cotton uniUs with Colouring Matttr. 



examined show tlie same uniformity of colour ; but in others of them 

 little oblong balls appear all along the inside of the tube, of the fine 

 pink shade of that dye, while the tube itself is colourless. 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 arrangement of 

 colouring matter in plants, in support of this view of the case. " Cel- 

 lular, tissue," says Dr. Lindley, in his Introduction to Botany, " gene- 

 rally consists of little bladders or vesicles of various figures, adhering 

 together in masses. It is transparent, and, in most cases, colourless ; 

 when it appears otherwise, its colour is caused by matter contained 

 within it." " The bladders of cellular tissue are destitute of all per- 

 forations, 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 vegetable 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 remarkably 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." Cot- 

 ton 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 where 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 trans- 

 parent solution of a brownish yellow colour, consisting of deoxidized 

 indigo combined with lime, and containing seldom more than j^^y of its 

 weight of colouring matter. By merely dipping cotton in this liquid, 

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

 tioned, within certain limits, to the length of the immersion ; and 

 all that is necessary then to render it blue is to expose it to the air. 

 Here an indifferent spongy substance exercises a power which over- 

 comes chemical affinity ; but the mixture which is formed of cotton 

 and indigo possesses none of the characters of a chemical compound. 

 We can only recognise in this action the same force, whatever that 

 may be, which enables animal charcoal to discolour similar liquids. 

 Charcoal, as we have also seen, withdraws metallic oxides from their 



