Prof. Lixpiey on the Anatomy of the Roots of Ophrydeæ, 425 
cettes are produced by the pressure upon them of the cells of parenchyma 
among which they lie. They are tough like horn, cannot be torn, crackle 
between the teeth like fragments of caoutchouc, and may be easily cut or 
even sliced, when they seem to be perfectly homogeneous, exhibiting no trace 
of layers or successive deposits, either when fresh, or after being dried, or 
when acted upon by ordinary chemical reagents. These nodules are mostly 
of about the same size, but here and there some are to be seen not larger 
than the ordinary cells of parenchyma. ‘The latter is thin-sided, in no degree 
pitted, and is readily coloured brown by the alcoholic solution of iodine or 
by exposure to air. Each cell bears with considerable regularity a cytoblast 
upon some part of its walls, and in most of the larger cells there is a small 
quantity of starch, readily coloured blue by the aqueous solution of iodine. 
Otherwise the parenchyma contains no solid matter, with the exception of 
occasional parcels of acicular raphides. 
The nodules are scarcely soluble in cold water, but when boiled they be- 
come tumid and partially dissolve into a transparent jelly, with a vitreous 
lustre. If exposed to the air they rapidly dry and become deep brown. The 
aqueous solution of iodine produces no sensible effect upon them in their na- 
tural state; but if they are first treated with caustic potash, or nitric or sul- 
phuric acids, all which dissolve their contents, they then acquire a deep claret 
colour when acted upon by alcoholic solution of iodine. 
But although iodine, in the form of the aqueous solution, while it colours 
blue the grains of starch, produces no sensible effect upon the nodules them- 
selves, yet it does produce an effect if the alcoholic solution is employed. 
In that case the nodules slowly become amethystine, altering to claret colour ; 
and if the nodules are wounded, the latter colour gradually, but slowly, ex- 
tends over the wound. These colours, however, soon disappear, especially if 
the air is warm ; not a trace of blue is at any time observable. The nodules 
are therefore not starch. Indeed I believe there is no known instance in 
which this common substance possesses even the organic characters which 
have been just described; nor am I aware of any other case of the solid 
secretions of plants assuming such an appearance as is found in the subject 
of these remarks. The cysts containing oily matter in the rind of the Orange 
are, in some respects, most analogous. 
3k2 
