PROCESSES WHICH OCCUR IN VEGETABLE TISSUES. 3 
If the plumule be amputated in the Bean-plant (Faba vulgaris, 
Mill.), the axis is reproduced by an adventitious bud; and the 
divided surface, if the plant be grown in the warm moist atmo- 
sphere of a greenhouse, is repaired in much the same manner, the 
new surface being formed by a layer of elliptical loosely arranged 
cells. 
On submitting sections of either to the action, first, of iodine 
solution, and afterwards of sulphuric acid, they stain throughout 
of a deep blue. In neither case does there occur any formation 
of cork in the surface of the injury. 
Frank observes, in the note before cited, that the new cells 
are indestructible by sulphurie acid, and are in this chemically 
different from the general parenchyma and resemble cork. But 
the repair in the case observed by him may have occurred 
under different conditions, since excess of moisture prevents the 
formation of cork, which is most readily produced in moderate 
dryness. In cases where the parts contain an abundance of sap, 
the process is modified by the formation of a scab of dry sap 
over the divided surface. For example, in .Ecbalium agreste, on 
amputating a young leaf close to the growing procumbent stem, 
a copious flow of sap occurs from the vessels of the vascular 
bundles, and quickly forming a pellucid drop on the surface, dries 
as a firm glassy film through which the cut surface remains for 
some days clearly visible. 
In the process of growth the layer of exuded sap is fissured, 
and the proper substance of the divided cells becomes exposed in 
its place. Ifthe removal be made quite early, and the parts be 
examined microscopically some weeks afterwards, scarcely any 
change may be found to have occurred in the elongated paren- 
chyma which forms the chief parts of such herbaceous stems 
and their subdivisions. Several layers of cells beneath the 
divided surface appear to be sharply outlined, and markedly 
different from the substance of the general parenchyma; but 
except at the very surface, these altered cells preserve their 
natural form. Beneath this encrusting layer, the cells may in 
some cases be found in certain spots less elongated, approaching 
toa flattened form; and in other cases, where the parts are 
allowed to attain full maturity, the living elongated cells have 
undergone oft-repeated divisions, so as thickly to cover the 
general tissue with cork and flattened subjacent phellogen. 
But before such a new formation has had time to occur, the 
