278 ABBEY, ON ORGANIC STRUCTURE. 
dyeing the nuclear matter. Now, Mr. Crum’s figures show 
the youngest fibres of cotton—in which the nuclear matter is 
most abundant—wholly undyed as regards the cell-wall, but 
with a beautifully coloured mass in the interior. This 
coloured substance very naturally puzzled Mr. Crum, who 
looked upon it as a mere precipitate of colouring matter, and 
he says, with reference to its shrinking, ‘It is remarkable 
that the alumina should adhere so slightly to the membrane 
which contains it, as thus to shift without difficulty from one 
part of it to another in the act of shrinking.” 
The fact is that the colour wholly depended on the presence 
of the nuclear matter, and that the mono-muriate of alumina 
was simply thrown away. 
Wrong conclusions will certainly be drawn from the ex- 
amination of preparations dyed with magenta unless they be 
washed until every trace of soluble colour is removed; and 
this should be done with alcohol. In the unwashed prepara- 
tion the nuclear matter is seen deeply coloured by the 
magenta. This operation should be followed by immersion 
in glycerine, which will remove any lingering trace of 
unattached colour, and which is also the best preservative 
fluid. If several vegetable sections of different kinds are 
steeped in the same colour-bath, care must be taken that 
none of them contain tannin, the mordanting power of which 
would altogether disguise the proper differentiating appear- 
ances conferred by the dye. 
I have omitted to remark, in the proper place, that 
secondary products, such as starch, are not coloured either 
by carmine or magenta. 
