RESEAEOHES ON PROTOPLASMIC CONTINUITY. 311 



trace any perforation of the cell wall by protoplasmic fila- 

 ments. 



The identification of the substance causing the reduction 

 now simply resolves itself into a micro-chemical investigation. 

 That it was a very powerfully reducing agent was evident from 

 the fact that gold chloride, silver nitrate, osmic acid, and 

 chromic acid were all reduced by the cell contents of a very 

 great number of the parenchymatous cells. When tested with 

 alcannin it was shown that the presence of resin was confined 

 to the laticiferous cells and to the cuticle, and there being no 

 oil globules in any of the cell contents, with the exception of 

 the latex, it was probable that the reaction with osmic acid 

 had not been caused by oil or fat. The chromic acid reaction 

 pointed to tannin. Sections were therefore treated with ferric 

 chloride, when the cells occupying the same position as those 

 which had especially reduced the osmic, chromic acid, &c., 

 were turned a brown-green colour, thus proving conclusively the 

 presence of tannin.^ 



In order to examine the distribution of the tannin cells, 

 transverse and longitudinal sections were treated with chromic 

 acid. They are shown to be present in the tissue in very great 

 numbers, and are especially abundant just under the epidermis 

 (at the very place where the greatest reduction of silver nitrate 

 occurs), and are arranged around the vascular bundle, being 

 also dotted about irregularly in the tissue. In longitudinal 

 section they are shown to be arranged in rows, end to end, 

 and their cell contents exhibit a fine reticulation. 



A longitudinal section of alcohol material treated with 

 chromic acid shows that tannin has escaped over the cut 

 surface, and thus gives confirmation to the other results. In 

 the reduction experiments I placed along with the Ficus sec- 

 tions, sections of material such as the endosperm of Phoenix 

 dactylifera, where I knew that perforation of the cell wall 



1 The tannin occurring in these cells is evidently not of the same character 

 as gallotannic acid which gives a black colour with ferric chloride. It is pro- 

 bably related to catechu-tannic acid, which also gives a brown-greeu when 

 treated with the above-mentioned reagent. 



