362 
NOTES AND MEMORANDA. 
existence or absence of this organ, wliicli can only be in my eyes a 
part fulfilling a very secondary glandular role. 
The use of reagents ba^ also enabled me to rectify several points 
relative to the structure of the disk and to the conformation of the 
digestive apparatus, of which I hope soon to publish the exact 
figures.” * 
Importance of the Vegetable Cell-walls in the Phenomena of Nutri- 
tion . — M. Max Cornu writes (in ‘ Comjites Rendus’); — “Sections 
of vegetable tissues sometimes extract the colour from solutions ; 
certain regions are brightly coloured, whilst others remain iincoloured. 
On immersing a transverse section of a monocotylcdonous stem in a 
weak solution of fuchsine, the sheaths of the fasciculi and the 
thickened walls colour brightly ; in ammoniacal carmine, to all ap- 
pearance of the same colour, the elements whicli are coloured are very 
different, being those which the sheath surrounds. 
Colouring matters, with sufficient power, are thus divided into two 
groups ; one being taken up by the thickened elements, the other not. 
The thickened elements are the woody fibres and cells of dicoty- 
ledonous plants, hypodermic fibres, certain vessels, certain fibres of 
the liber, the sheatli of monocotyledonous fasciculi, and generally the 
most external part of the cuticle ; but these elements must be full 
grown. 
The elements of the other group are young or thin, and generally 
covered with only a thin layer of protoplasm : these are the cells of 
the cambium, scalariform vessels, the collenchyma, &c. The ordinary 
cells, the vessels, and other elements may, according to the plants or 
the part of the tissue, be classed in one or the other category. 
The distinction of these two groups is easily obtained by means of 
sections of herbaceous stems of dicotyledons or of monocotyledons ; 
it is well to destroy the contents of the elements by acetic acid and to 
emjjloy weak solutions. 
The fixing of the colouring matters depends on the relative density 
of the wall ; we get only an imperfect idea of this density from the 
colour and refraction. It is possible to follow by means of these 
reagents, the accumulation of new substance in the wall ; the re- 
sorption of this wall in the spiral vessels of the fasciculi in process 
of elongation (Umbelliferge, Cucurbitacese, &c.) is also easily 
observed. 
The ordinary chemical reagents easily show that the colouring 
has no relation to the chemical composition ; I have been able to 
study with this end, the pure products of M. Fremy (cutose, 
vasculose, cellulose), separated from the mass of complex substances. 
From a physical point of view these data were wanting. 
We know the importance of the cell-wall in the interchange be- 
tween the cells and the ascent of liquids ; the experiments of M. 
Jamin have sliown the value of certain physical forces, and notably 
of imbibition. But more than that, the walls may be the reservoirs 
in which are accumulated certain soluble principles drawn up by the 
* ‘ Comptes Rendus,’ vol. Ixxxvii. p. 537. 
