410 MR. SPENCER ON CIRCULATION AND 
have in some cases been supplied to the roots for their absorption, are obviously so un- 
like the matters ordinarily absorbed that they are likely to interfere fatally with the 
physiological actions. If experiments of this kind are made by immersing the roots in 
a dye, there is, besides the difficulty that the mineral mordant contained by the dye is 
injurious to the plant, the further difficulty that the colouring-matter, being seized by 
the substances for which it has an affinity, is left behind in the first layers of root- 
tissues passed through, and that the decolorized water passing up into the plant is not 
traceable. To be conclusive, then, an experiment on absorption through roots must 
be made with some solution which will not seriously interfere with the plant’s vital 
processes, and which will not have its distinctive element left behind. To fulfil these 
requirements I adopted the following method. Having imbedded a well-soaked broad 
bean in moist sand, contained in an inverted cone of card-board with its apex cut off 
for the radicle to come through—having placed this in a wide-mouthed dwarf bottle, 
partly filled with water, so that the protruding radicle dipped into the water—and having 
waited until the young bean had a shoot some three or more inches high, and a cluster 
of secondary rootlets from an inch to an inch and a half long—I supplied for its absorp- 
tion a simple decoction of logwood, which, being a vegetal matter, was not likely to 
do it much harm, and which, being without a mordant, would not leave its suspended 
colour in the first tissues passed through. To avoid any possible injury, I did not 
remove the plant from the bottle, but, slightly raising the cone out of its neck, I poured 
away the water through the crevice and then poured in the logwood decoction; so that 
there could have been no broken end or abraded surface of a rootlet through which the 
decoction might enter. Being prepared with some chloride of tin as a mordant, I cut 
off, after some three hours, one of the lowest leaves, expecting that the application of 
the mordant to the cut surface would bring out the characteristie colour if the logwood 
decoction had risen to that height. I got no reaction, however. But after eight hours 
I found, on eutting off another leaf, that the vessels of its petiole were made visible as 
dark streaks by the colour with which they were charged—a colour differing, as was t0 
be expected, from that of the logwood decoction, which spontaneously changes even by 
simple exposure. It was then too late in the day to pursue the observations ; but next 
morning the vessels of the whole plant, as far as the petioles of its highest unfolded 
leaves, were full of the colouring-matter; and on applying chloride of tin to the cui 
surfaces, the vessels assumed that purplish red which this mordant produces when 
directly mixed with the logwood decoction. Subsequently, when one of the cotyledons 
was eut open by Prof. Oliver, to whom, in company with Dr. Hooker, I showed | 
specimen, we found that the whole of its vascular system was filled with the decoction 
Which everywhere gave the characteristic reaction. And it became manifest that the 
liquid absorbed through the rootlets, in the central vessels of which it was similarly 
traceable, had part of it passed directly up the vessels of the axis, while part of it p 
Bae ketone other vessels into the cotyledon, out of which, no doubt, we 
bui SONS OMA pubs charged with a supply of the stored nutriment. su 
OE a verification by varying the method. Digging up some young P 
(Marigolds happened to afford the best choice) with lar und ther» 
ge masses of soil ro 
