256 MR. C. DARWIN ON THE ACTION OF CARBONATE 
and they generally arose from cells destitute of granules; yet in 
many places whole groups of cells abounding with granules gave 
rise to well-developed root-hairs. "Therefore the rule which holds 
good with so many plants, namely, that root-hairs arise exclu- 
sively from colourless cells destitute of granules, here quite 
breaks down. The granules extend from the cells into the hairs 
which spring from them, as is shown in fig. 2; and they here 
sometimes become confluent, forming rounded or elongated 
masses of transparent green matter. This matter within the tips 
of some of the hairs seemed to pass into a brownish fluid. It 
was repeatedly observed that where many hairs rose close 
together from cells containing the green granules, the tips of the 
hairs were glued together by cakes or masses of orange-coloured 
translucent tough matter. This matter could be seen, under 
favourable circumstances, to consist either of very thin homoge- 
neous sheets or of aggregated granules. It was not acted on by 
an immersion of two hours in absolute alcohol or in sulphuric 
ether. The smaller globules were either dissolved or destroyed 
by sulphuric acid, while others were rendered highly transparent. 
The formation of this orange-coloured matter is independent 
of the previous action of ammonia; and I have noticed similar 
matter attached to the rootlets of many other plants. It is pro- 
bably formed by the softening or liquefaction of the outer sur- 
face of the walls of the hairs, and the subsequent consolidation 
of the matter thus produced $. Nevertheless some appearances 
led me to suspect that the brownish fluid which was seen within 
the tips of the hairs enclosing the green granules may perhaps 
exude through the walls, and ultimately form the cakes of orange 
matter. 
A few other solutions were tried. Roots were left for from 
20 to 43 hours in a solution of 7 parts of pure carbonate of soda 
to 1000 of water, and in no ease were granules deposited in the 
exterior cells; but some of these cells in longitudinal rows 
became brown ; these alternated with rows of colourless cells. In 
one instance several of these cells included oval or spherical masses 
of an apparently tenacious fluid of a brown tint. Single cells in the 
parenchyma likewise became brown; others were dotted, like a 
mezzotinto engraving, with barely distinguishable granules, whicb, 
* See some remarks on this liquefaction of the outer surface of root-bairs by 
my son Francis and myself in ‘The Power of Movement in Plants, 1880. 
p. 59, 
