Holden.— -Some Wound Reactions in Filicinean Petioles . 787 
large mature petioles, the reaction was quite different, and was similar 
to that constantly resulting in Davallia polyantha and Adiantum spp. 
Here the peripheral cells became brown and enormously thick-walled with 
large pits for protoplasmic connexions, the thickening becoming less pro- 
nounced as the cells became further from the wound until they merged into 
the normal cortical parenchyma (PI. LXXIV, Fig. 12). 
Microchemical investigation demonstrated that this thickening was 
also peculiar in consisting throughout of pure cellulose. As in previous 
cases, the outermost cells showed a solid deposit of gum, whilst those near 
the exterior also showed large quantities of granular matter. 
The reaction produced in Scolopendrium vulgar e, which is soft bodied 
and possesses an undivided leaf, was exceptional. The parenchymatous 
cells extending through fully half the diameter of the cortex, and in some 
specimens even partially round the vascular bundle, had, under favourable 
circumstances, without actually dividing, elongated to a very considerable 
extent, producing exaggerated intercellular spaces owing to the partial 
separation of adjacent cells (PI. LXXIII, Fig. 9). The result of this lengthen- 
ing is that a slight intumescence is formed, comparable to those produced 
as a consequence of traumatic stimulus in the case of many roots (Nemec ( 20 ), 
Bayliss (1), Davis ( 7 )). 
No amitotic nuclear divisions were observed, though the majority of 
those in the cells affected were spindle shaped, and some showed a median 
constriction (PL LXXIII, Fig. 10). The number of cells which were com- 
pletely filled with gu m was exceptionally large, these extending inwards to 
a depth of six or more, and, as in previous cases, the cells below also showed 
abundant granules. 
From these facts it will be perceived that there is in the pinna-bearing 
region a distinct loss of cambial activity, the bulbil-producing species of 
Asplemum , Polystichum , and Woodwardia being the only ferns among those 
examined which still show any marked efforts in this direction. 
The tissues developed during the formation of * pneumathodes ’ which 
characterize the rhizome and stipules of the Marattiaceous ferns as figured by 
Hannig ( 12 ), offer a remarkable analogy to those produced in the wounded 
areas in the pinna-bearing parts of the bulbiferous species referred to. 
In the remaining species examined the general mode of response takes 
the form of local thickening, either of cellulose, ligno-cellulose, or lignin, 
of the tissues at the seat of injury, this being accompanied by a greater or 
less amount of cell-elongation and division, and an abundant deposit of 
gummy matter. 
(iii) In the petiole below the region of pinna-insertion, the tissues 
of which may be regarded as quite mature, there is an almost uniform 
response to wounding. Here there is no elongation of the cortical elements 
in normal cases, thickening and the production of gum in large quantities 
3 F 2 
