STRUCTURE.] SUGAR GUM. 129 



have not hitherto been able to find it again, although I have 

 applied an infinite variety of mixtures of the three re-agents, 

 and also used the hydrochloric acid first and the others after- 

 wards, or these first and that last. It is possible that a 

 peculiar stage of the life of the cell may be here requisite, 

 which, therefore, I have not again lighted on. I remark, 

 however, expressly that I found this changing of colour in 

 all the blue-coloured cells of those two cells, and consequently 

 it cannot be attributed to any optical illusion, and the less so 

 because I could continue this play of colour as long as I 

 liked/' 



2. Of Gum and Sugar. 



Under the influence of vital force starch changes into 

 gum and sugar. Sugar makes its appearance as a transparent 

 fluid, which seems as clear as water, and is not rendered 

 turbid by alcohol, but is coloured brown by tincture of 

 iodine, according to the greater or less degree of dilution of 

 that agent. 



Gum appears as a yellowish, more consistent, less trans- 

 parent fluid, which, with tincture of iodine, coagulates into 

 a pale-yellow colour. When vegetation has advanced to that 

 point that gum is the latest immediate product, there appears 

 in it a great many minute molecules, which are generally so 

 small as to resemble dark points; at that time the fluid 

 becomes a darker yellow upon the application of iodine. 

 But the molecules, if they are large enough to show their 

 colour, become dark-brown yellow. It is this mass, so 

 transparent that it can hardly be seen till it is coloured, in 

 which, in all cases, organisation commences, and from which 

 the youngest structure is constituted. It may be called 

 Vegetable Jelly, and is probably nearly the same as Pecten, 

 the base of Gum Tragacanth, and many other kinds of 

 vegetable mucus. It is this jelly, which, by a further 

 chemical alteration, becomes the membrane of cells, and is 

 afterwards the material by which they are thickened. 



Vegetable mucilage of the chemist in part (Bassorine ; 

 Salep) is a horny or cartilaginous substance, when dry ; 

 when moist, it swells up in a gelatinous manner, and becomes 



VOL. I. K 



