Holden . — Some Wound Reactions in Filicinean Petioles. 783 
w.s. 
SCL. 
SCL. 
virginica , in which only a single layer of cortical cells, namely, that 
consisting of the uninjured units immediately below the wound, exhibits any 
activity. This layer elongates quite appreciably, but generally shows no 
trace of cell-division (PL LXXIII, Fig. 4). 
The superficial resemblance of these cells, both in Polystichum angulare 
and in the species which have previously been described, to the intumescences 
produced on the leaves of Hibiscus and other forms (Dale, 5 , 6), led to 
a careful investigation of their cytology with a view to ascertaining whether 
there were any induced pathological nuclear phenomena. In a few 
cases cells were found to contain two nuclei, almost invariably in close 
proximity to one another, and in a considerable number of cells nuclei 
of abnormal shape, often showing a median constriction, were noticed 
(PL LXXIII, Fig. 10). 
In Osmunda regalis, Blech- 
mini brasiliense, and Struthio- 
p teris german ica , which serve to 
illustrate the last gradation of 
wound response, there is very 
little or no elongation of the 
individual cells, and only very 
rarely a transverse division, 
but the outermost cells de- 
velop very early a strong su- 
berization of their walls. These, 
and others of the hardest- 
bodied forms, also show a 
band of lignified tissue im- 
mediately above the vascular 
structures, which, though dif- 
fering in structural detail from the sub-epidermal sclerenchyma, serves 
largely to replace this tissue as a protective sheath on the injured side 
(Text-figure). 
From the foregoing examples it will be seen that a distinct and 
gradual series of forms is traceable, commencing with those producing 
a perfect pad of healing tissue such as Asplenium Belangeri and Polystichum 
proliferum , and passing through forms like Lastraea Filix-mas , with cell- 
elongation and the production of an incipient cambium, to forms like 
Polystichum angulare , with cell-elongation alone, and finally to types like 
Osmunda regalis , in which cell-elongation and division are very infre- 
quent, and where these are replaced by an efficient suberization and lignifi- 
cation. 
The secondary changes which occur in the wounded apical areas as 
these unfold and become mature were found to be extremely variable, 
Text-figure. Transverse section, young petiole of 
Osmunda regalis. SCL., sub-peripheral sclerenchyma; V.B., 
vascular bundle; W. s., wound-surface; s. s., suberized 
cells ; LIG., cortical cells, secondarily lignified. 
