42 On Plants absorbing coloured infusions by their roots, 



growth was impeded ; but as the plants lived, I, after a week, ten 

 days, or even a fortnight, dissected them, viewed the parts in every 

 light, by every commandable power of glass, in water and without 

 it. Under every circumstance, not a particle of the colouring 

 matter appeared in any spot, cell, or vessel, throughout the stem. 

 Having mentioned this (in passing), while writing on vegetable 

 food, a writer in reply, asserted that, if I had employed madder, I 

 should have detected the colour which would have passed. I soon 

 recollected that Sir H. Davy had mentioned that dye ; and on 

 referring to page 245 of the Sixth Agricultural Lecture, read, that 

 " the radical fibres of plants made to grow in infusions of madder 

 are tinged red ;" but this is saying just nothing, as to the point 

 insisted on, for the mere dyeing or tinting of the parts inserted 

 in the liquid, affords no evidence of the ascent of that liquid : but 

 he adds " that substances which are even poisonous to vegetables 

 are absorbed by them." This latter assertion bears upon the 

 enquiry, and to set it at rest I employed three modes of investigation. 



July 18, 1834, 1 took three large cuttings of clear white stemmed 

 Balsams, placed each in a phial of pure water, and set them close 

 against the side glass of the east end of my stove ; no bottom heat 

 was used, nor was shade interposed. In a few days, processes were 

 formed at the bases ; in ten days ( 28th) the three plants had per- 

 fect, white, numerous roots. I lifted them carefully one by one 

 out of each phial, and planted them successively in as pure, simple, 

 sandy loam as I could select ; not admitting a known particle of 

 decomposable matter, into the soil. I gave water only for a day 

 or two, shading the plants, till I felt sure that vegetation was 

 active ; but they never shrank, and were covered with blossom buds ; 

 the greater number of which, were pinched off; the pots were 

 small sixties. 



1st. Two solutions had been prepared, one of a drachm of 

 powdered Brazil wood, in four ounces of water, adding four or five 



