7 84 Holden. — Some Wound Reactions in Filicinean Petioles. 
and to tend, in ultimate effect, towards the condition resulting from 
wounds of the second order, that is, those within the region of pinna- 
insertion. 
In the bulbil-producing forms there were very marked changes : the 
cambiform cells had evidently ceased to divide and had become decidedly 
more thick-walled (PL LXXIV, Fig. 19), this thickening proving to be of a 
purely cellulose nature, whilst, in addition, the whole of the cortical tissues on 
that side of the stele adjacent to the affected surface had become filled with 
a gummy deposit (PI. LXXIV, Fig. 20 b). This intracellular gum deposition 
was also a characteristic feature of all the remaining species, whether the 
cambial response had been still fairly strongly in evidence or not. 
The gum, even in the fresh material before preservation, was extremely 
thick and viscous, especially in the outermost cells of the affected region, and 
on fixation and hardening in alcohol was found to have become quite 
solid. The slight shrinkage of the cell-contents had, in many cases, caused 
the solid gum to crack and furrow, so providing a ready means of recog- 
nition. 
The process of secretion of this substance in the cells could be fol- 
lowed with ease, since the earlier stages were shown in the specimens 
which had only been allowed to grow for a comparatively brief period 
after wounding, and also in the deeper seated cells of the maturer speci- 
mens. From these it could be seen that the secretion was first produced as 
minute granules or globules in the cytoplasm, these gradually becoming 
larger and ultimately coalescing to produce an almost solid deposit. 
This substance, which is presumably of a protective nature, gives the 
following reactions characteristic of wound gum : 
1. It is insoluble in alcohol, chloroform, or benzol. 
2. It is insoluble in hot or cold concentrated H 2 S 0 4 . 
3. It is insoluble in hot or cold concentrated solution of KOH. 
4. It stains deeply with alkannin, and with ruthenium red. 
Treatment with thymol, orcinol, and phloroglucin gave, however, 
entirely negative results. It differs from wound gum also in the fact that 
it is intracellular, and does not appear to be due to any tissue degeneration, 
since even the cells in which the deposition is most complete show no 
traces of disintegration, and the nuclei do not appear to be adversely 
affected. 
The cell-walls in the gum-secreting zone invariably increase in thick- 
ness, but this, in different forms, and even different specimens of the same 
form, varies considerably in its microchemical reactions. 
In practically all species the outermost cells gave a pure cellulose 
reaction with chlor-zinc-iodine, and absolutely negative results with phloro- 
glucin and HC 1 , and other lignin-demonstrating reagents. This is easily 
understood in those petioles where the cells show elongation and division, 
