ROUTS ОҒ ACONITES. 129 
sieve-tube strands, and of strands of the vasal elements of the xylem. This differentia- 
tion may already be observed with the naked eye or at any rate with a good pocket-lens. 
Sclerenchymatic cells may be added in certain species in the outer zones of the 
central cylinder, but they never become prominent with the exception of А. feroz. 
I have already pointed out that the modifications which allow us to distinguish 
several types in the structure of the root-tubers of Aconitum may be traced back to the 
disposition of the cambial tissue. Тһе simplest case is represented by what Goris has 
called the Napellus type, to which the commonest kind of * bikh roots” sold in the 
Bengal bazaars and imported into Europe belongs, namely that which is derived from 
A. spicatum. Here, as in the European A. Napellus, the cambium appears in cross- 
section as a faint more or less sinuous ring. Without it we notice, scattered through 
the otherwise homogeneous tissue, minute dots which correspond to delicate strands 
composed essentially of sieve-tubes, whilst we find inside the cambium ring, and close 
to it, semilunar or horseshoe-shaped marks, or minute radially directed dashes and 
dots, the cross-sections of the vasal strands of the xylem, Where they are not very 
clear they сап be made more conspicuous by the phloroglucin and сШотіс acid reaction 
to which they respond very readily, staining deep purple. The cambium line 
itself is so delicate that it would not be seen, except under a high power, but for 
the presence of zones of а more small-celled and compact tissue on both sides of it, 
and similar conditions contribute to the more prominent marking of the xylem strands, 
introducing a contrast of denser and looser parts into the otherwise uniform tissue. 
The whole of the central cylinder outside the cambium zone may practically be considered 
as consisting of secondary phloem in which the primary phloem is lost, whilst the 
tissue within the cambium and the xylem strands,—pith by origin and storage 
tissue by structure and function—conforms to the parenchyma of the secondary 
phloem. The same structure is repeated in the tubers of A. soongaricum, chasmanthum, 
violaceum, Faleoneri, spicatum, laciniatum, ferax, heterophyliotdes, — leucanthum, dissectum, 
and the “Jadwar” tubers, to whatever species they may belong. Further modifica- 
tions are introduced into this type by the varying colour and the more or less 
“ farinaceous? or horny or cartilaginous appearance which the tubers assume when dried— 
conditions difficult to trace as to their ultimate cause; by the more or less prominent 
development of the cambial zone and the xylem strands; and, in the case of A. feroz, by 
the formation of sclerenchymatic sheatis encasing the sieve-strands in the mother-tubers. 
These differences are mentioned in the descriptions of the species, and I need not dwell 
on them here, the less so, as they are perhaps not quite reliable, the number of 
observations from which they have been derived being in most cases very small. 
Besides, there are other characters, especially the differences in the taste of tubers, 
due to the presence of different alkaloids, that afford a better help for discrimination 
within this group. | 
The second type, of which I may quote Л. heterophyllum as an example, exhibits an 
essentially different structure. We find, in place of one continuous cambium ring, 
several (up to six) small rings or irregular stars embedded in a uniform tissue, and 
generaily arranged in a concentric ring. Sieve-strands occur not only outside this ring, 
but also within it, surrounding the little rings or stars; but they are usually so delicate 
that the compound microscope is required to see them. Inside the small cambium rings 
the lignified portions of the xylem may be observed as more or less V-shaped marks 
which almost meet in the centre. This structure aleo needs higher magnification to 
