NOTES AND MEMORANDA. 
368 
root ; it is tlins easy to understand that the sap may be almost 
pure water, and that it could scarcely concentrate itself in the upper 
parts of the j)lant, subjected during summer to a considerable evapo- 
ration. The theory of the descending sap and the other theories left, 
in this respect, grave difficulties unsolved. 
As to the substances vvliich do not fix themselves on the walls of 
the elements, we imagine therefore that they must circulate in the 
plant in a very different manner. There is then a distinction to 
establish from a physical point of view, with reference to the cell- 
wall, in the absorption and the migration of the substances dissolved. 
One of the groups of colouring substances contains (in the order 
of the colours of the spectrum) : — 
Aniline black, hematoxyline, Coujiier’s blue, osmic acid, cyanide of 
iron, aniline blue, rosollic acid, ammoniacal carmine, juice of phyto- 
lacca, &c. 
The other contains ; — 
Methyl-violets and quinoline violet, diphenylamine blue, aniline 
green, Coupier’s green, aniline yellow and brown, permanganate of 
potash, coralline, sulphocyanide of iron, fuchsine, rosonaphthaline, &c. 
These properties may be utilized, in approximate analyses, to eli- 
minate easily certain substances sought for (in wines, syrups, &c.), or 
to concentrate them. 
The sulphocyanide of iron acts upon the thickened elements (like 
the perchloride) and colours them the colour of dragon’s blood ; never- 
theless a similar section rapidly loses colour in the cyanoferride of 
potassium, and precipitated cyanide of iron acts upon thin and plas- 
matic elements. It is seen that the secondary reactions may much 
modify the primitive distribution of the substances. In experiments 
on nutrition, reactions of this kind may give rise to errors. 
The protoplasm and the nuclei of the elements when dead are 
rapidly coloured by the substances which act on the thick parts ; but 
the whole easily loses colour. The substances of the other group 
colour more slowly, but in a more permanent manner, the nucleus 
especially. Experiments made in collaboration with M. Mer have 
enabled us to understand this fact. 
The explanation of these phenomena of fixation are based on a 
physical action very similar to capillarity ; the dimensions of the 
molecules and their interval ought probably to be considered : but 
this is not the place to dwell upon it. 
To sum up, we see that physical forces may separate the matters 
absorbed by the plants from one another, according to a law easily 
demonstrated experimentally with coloured substances : very import- 
ant consequences in regard to the phenomena of nutrition may be 
deduced therefrom.”* 
Mechanism for the Fertilization of Meyenia erecta. — Mr. R. Irwin 
Lynch, of Kew, describes, in the ‘ Journal of the Linnean Society,’ a 
previously unobserved mechanism in this plant (an acanthaceous shrub 
of tropical Africa) for cross-fertilization. The anthers, which are 
* ‘ Comptes Renclus,’ vol. Ixxxvii. p. .S03, 
2 V, 2 
