134 
Holden . — Wound Reactions in Pteris. 
Appendix. 
The phenomenon of local delignification in the sub-epidermal scle- 
renchyma is so characteristic and so unexpected a feature of wounds of all 
types, that a few remarks on the methods employed are perhaps advisable. 
It was found that the discoloration of the cells interfered with the micro- 
chemical study of the tissues, and it was therefore removed by treatment 
with eau de javelle. For this purpose the section to be studied was 
mounted in a drop of that liquid, and heated on the slide over a Bunsen 
flame. As a rule, from five to ten seconds of this treatment were sufficient 
to remove all colour. A little fresh eau de javelle was then added to 
dissolve the crystals formed by the partial evaporation of the first supply, 
and the whole was then absorbed with filter-paper. The section was next 
treated with a series of drops of spirit until all traces of the eau de javelle 
were removed. (About twenty drops successively applied and absorbed 
were found to work well in practice.) It was then treated with either 
chlor-zinc-iodine or with phloroglucin followed by either HC1 or H 2 S0 4 . 
The walls referred to as delignified invariably gave a positive cellulose 
reaction with chlor-zinc-iodine, and a negative lignin one with phloroglucin 
and acid. It appears to be a general impression 1 that treatment with eau 
de javelle has a delignifying effect on plant tissues, and this is probably the 
case after more prolonged treatment, but the establishing of efficient con- 
trols demonstrated that no error had arisen from this source. In the first 
place, the whole of the sub-epidermal sclerenchyma remote from the wound 
and the xylem elements in the stele gave with phloroglucin a positive 
reaction after treatment, indistinguishable from that given by untreated 
sections, whilst sections of uninjured Pteris petioles, after identical treat- 
ment for the short time necessary in these experiments, showed no 
difference in their reactions. Other control experiments were made with 
the young stem of Lycopodium alpinmn , in the thickened cortex of which 
the lignification is incomplete. In such specimens, treatment with phloro- 
glucin and an appropriate acid produces a pink (ligno-cellulose) rather than 
a red coloration, and it was found here also that the brief period of treat- 
ment with eau de javelle had no delignifying effects. It will thus be seen 
that the inference that delignification is a traumatic response is amply 
justified. 
1 Cf. Zimmerman, Botanical Microtechnique : Cavers, Pract. Botany, &c. 
