104 Mr W. Gardiner, On the constitution [Feb. 11, 



for lignified tissue they both stain in a similar manner. There 

 can in fact be little doubt that here the middle lamella has under- 

 gone lignification. In the same way in suberised or mucilaginous 

 membranes, the middle lamella undergoes the same changes as 

 the cell- walls. With regard to the mucilaginous change, it may 

 be noticed that the middle lamella may be at once converted into 

 mucilage as in the parenchyma cells of the petiole of Aucuba 1 ; 

 or as Prillieux 2 remarked in the formation of gum in the cherry, 

 the lamella may be at first dense and resistant, in which case the 

 mucilage appears between it and the last layer of cell-wall. 

 Consequently it only subsequently becomes mucilaginous. 



The great point with regard to middle lamellas other than cel- 

 lulose is that in their substance the maximum amount of change 

 appears to have taken place — that is to say — almost the whole of 

 the cellulose has been converted into lignin, cutin, or mucilage, as 

 the case may be, and thus but little of the cellulose framework 

 remains. This will of course explain the fact that after treatment 

 with Schultze's mixture or other oxidizing agents, the various cells 

 readily separate from one another, for now practically the whole 

 of the middle lamella has suffered solution, and, of the cells, it 

 is only the cellulose framework which remains. 



Tt would thus appear that in unaltered cellulose walls the 

 middle lamella consists of dense cellulose; while in lignified cuti- 

 cularised corky or mucilaginous cells, the changes which occur in 

 the middle lamella are of the same character as those of the rest 

 of the membranes, and have moreover reached their maximum. 



Additional Note. 



I should like to add here a few remarks with regard to the 

 continuity of the protoplasm through the walls of vegetable cells. 

 Since my last publication upon that subject, a paper has appeared 

 in the February number of the Journal of Botany 3 in which the 

 writer states that in the Florideae there is a communication 

 between the contents of adjacent cells, which so far as one can 

 judge from the text, is typically brought about by means of open 

 pits, although in certain instances, e.g. the older cells of Polysi- 

 phonia fastigiata, a delicate diaphragm may be present. 



1 In such instances the cells separate by mere treatment with hot water. The 

 well known case of the separation from one another of the cells of Potato tubers 

 when boiled is another example. When on the other hand the mucilage or gum 

 is combined with bases, e.g. in case of Calcium Pectate, an acid is required to 

 bring about the isolation of the cells. 



2 Prillieux, loc. cit. 



3 Hick, Protoplasmic Continuity in the Florideae. Since I find (March 17th) 

 that in the remaining part of his paper, which appears in the March number of the 

 same Journal, he has in no way altered his opinion, I have nothing to add to 

 my former remarks. 



