316 WALTER GARDINER. 



Professor Frommann's mistakes in this direction I might sug- 

 gest with regard to the occurrence of chlorophyll grains in the 

 cell walls that he was looking down through the thickness of 

 a cell wall upon a chlorophyll grain that had got into a pit ; 

 and in the case of the grain in the cuticle^ I can only put 

 forward the explanation that he was viewing a chlorophyll 

 grain in the guard cell of a stoma through the cuticle of an 

 epidermal cell. 



There is the simpler view, that during swelling, and also by 

 mechanical means, some of the protoplasm was carried on to 

 the cut surface of the cell wall ; and fig. 4, Plate I, which re- 

 presents a subepidermal cell of Dracaena, certainly gives some 

 colour to this idea, although I put it forward with some diffi- 

 dence. Numerous preparations, treated and stained in various 

 ways, showed no sign of there being either granules or nets, or, 

 finally, any protoplasmic structure whatsoever in the intercel- 

 lular spaces. 



Now, as to the subject of holes, gaps, and crevices in the cell 

 wall. At the outset I cannot but feel that Professor Frommann 

 was somewhat unfortunate in taking for his investigation such 

 small-celled tissue as occurs in the leaves of Dracaena and 

 Rhododendron, and especially so as regards the epidermal 

 cells. In both these leaves, and particularly in Rhododen- 

 dron, the epidermal and parenchyma cells are very freely 

 pitted, and it is quite evident that what Professor Frommann 

 has taken for open passages between the cells are in reality 

 ' pits, each of which is closed by its own pit membrane. In 

 Plate II, figs. 4 and 5, he gives a drawing of the so-called 

 holes, but even a cursory examination of carefully ])repared and 

 thin sections treated with Chlor. Zinc lod., or otherwise appro- 

 priately stained, will at once convince one that in every case a 

 closing membrane is present, and that the pits are not open. 

 As I have mentioned in the earlier part of this paper, the 

 occurrence of open pits in living cells would be quite opposed 

 to our accepted ideas of cell structure and cell mechanism. In 

 his descriptions, however, Professor Frommann gives passages 

 which suggest that he has noticed, but not identified, the pit- 



