Further Observations on the Wound Reactions of the 
Petioles of Pteris aquilina. 
BY 
H. S. HOLDEN, M.Sc., F.L.S., 
Lecturer in Botany , University College , Nottingham. 
With four Figures in the Text. 
I N 1912 I recorded in this journal 1 some observations on the wound 
responses of filicinean petioles. Whilst in Cumberland during the 
summer of 1914 the opportunity was taken of collecting material of Pteris 
aquilina , in which specimens showing wound-scars of greater or less extent 
are not uncommon. This material was supplemented by a further supply 
collected at Oxton (Notts.). Specimens such as these suffer, of course, 
from the disadvantage that one cannot determine either the cause of the 
injury or the age of the wound, but, on the other hand, they afford some 
evidence as to how far the wound response exhibited under natural con- 
ditions agrees with the results obtained experimentally. The injured 
petioles may be grouped, for purposes of description, under two heads as 
follows : 
(i) Those in which the wound did not penetrate below the sub-epidermal 
sclerenchyma. These were very common. 
(ii) Those in which the sclerenchyma had been penetrated. The 
wounds of this second type naturally varied in severity, and in some cases 
were fairly deep seated. 
Whilst differing in points of detail, the whole of the specimens examined 
showed a certain number of well-marked features in common, namely : 
(i) The occurrence of a bright yellow substance in the walls of the 
zone of cells abutting on the wound. This discoloration, which was due to 
the deposition of a tannin-like substance, 2 became more pronounced and 
darker in tint in the most superficial layers. 
1 Holden, H. S. : Some Wound Reactions in Filicinean Petioles. Ann. Bot., 1912, p. 777. 
2 It gives a greenish-black coloration with neutral ferric chloride, and a red coloration with an 
aqueous solution of iodine in KI mixed with a little 10 % ammonia. (Cf. Haas and Hill, Chemistry 
of Plant Products, pp. 190-7.) 
[Annals of Botany, Vol. XXX. No. CXVII. January, 1916.] 
