ABBEY, ON ORGANIC STRUCTURE. 277 
nothing more. But other vessels will be seen, where the 
spiral fibre is but faintly mapped out; and these contain 
nuclear matter—the scaffolding of the unfinished structure. 
This is also seen, though not to such advantage, in the 
transverse section. Does not this suggest a compromise 
between opposing opinions as to the function of the spiral 
vessels? It is evident that they cannot convey air when 
young and filled with nuclear matter; but this objection 
disappears with age. 
If I might venture to suggest yet another hypothesis, it 
would be, bearing in mind the early appearance of the spiral 
fibre, that it serves the simple mechanical purpose of giving 
that elasticity to the whole structure, which must necessarily 
be given in some way or other. 
In the ‘ Micrographic Dictionary’ we are told, apropos of 
the epidermis of plants, that “ the walls of the cells next the 
external surface are found much thicker than the rest, 
this thickening extending more or less down over the con- 
tiguous side walls. When such sections are treated with 
sulphuric acid and iodine, the greater part of the thickness, 
from without inward, of this outer wall is stained yellow, 
while the rest of the walls assume the blue colour ordinarily 
taken by cellulose with these reagents.” 
Magenta gives a beautiful and instructive variation of 
this experiment, dyeing only that part which iodine colours 
yellow. Probably this state of things is not so universal as 
inferred by the ‘Micrographic Dictionary,’ for, in some 
plants, e.g. asparagus, the epidermal cells are altogether 
uncoloured, while the superjacent cuticle is deeply stained. 
These facts have an important bearmg on the cellulose 
question, on which I would fain have touched, but must for 
the present forbear. 
Before coming to the final full-stop, some notice seems to 
be demanded by a paper by Mr. Walter Crum, which 
appeared in the ‘ Chemical Society’s Journal’ for 1863, and is 
entitled “On the manner in which Cotton unites with 
Colouring Matter.” This only byaccident; for,since the paper 
is principally concerned with the actions of mordants, it would 
hardly have been available in this place, were it not that one 
of the substances quoted as a mordant is, as it seems to me, 
no mordant at all. The dye principally spoken of in Mr. 
Crum’s elaborate and carefully illustrated essay is madder, 
and the so-called mordant in question is the mono-muriate 
of alumina. My own experiments have shown me that the 
colouring principle of madder has the same powers as carmine ; 
that is to say, it is capable, without the aid of mordants, of 
