RESEAEOHES ON PROTOPLASMIC CONTINUITY. 315 



fessor Frommann, although I am unable to see the nets and 

 reticula with anything like the clearness with which he de- 

 scribes them in his paper, and figures them in his drawings. 

 There is, however, a distinct reticulation in the cells of both 

 Rhododendron and Dracaena, especially in the former. 

 This reticulation is shown much more clearly by staining with 

 haematoxylin, tissue that has been preserved in picric acid, and 

 afterwards washed with alcohol. In Rhododendron very 

 many of the cells, and especially the pallisade-parenchyma cells, 

 contain tannin, and in these the reticulation is especially evi- 

 dent. I have frequently found this to be the case with tannin 

 cells in general. Treatment with chromic acid, osmic acid, 

 dilute potash, or dilute nitric acid will generally bring out a 

 reticulate structure, although at present I am unable to give 

 any explanation of the phenomenon. My attention was first 

 drawn to the fact when investigating the tannin cells which 

 occur in the pulvinus of Robinia pseudacacia. 



As far as regards the reticulate structure, I can, therefore, in 

 the main bear out the statements of Professor Frommann, whose 

 results certainly accord with those of Schmitz^ and Strasburger f 

 both these investigators having established that a reticulation 

 can be observed in the protoplasm and the nucleus. The 

 chlorophyll grains in the same way exhibit reticulation, but I 

 should like to point out, as I did in the case of Dr. Elsberg^s 

 research, that they are much swollen and somewhat disorganised 

 by the action of dilute glycerine. Nevertheless, after the most 

 careful preparation with picric acid and absolute alcohol and 

 subsequent staining, they still exhibited a distinct reticulate 

 structure, and agree fully with the description given by 

 Pringsheim^ of the structure of chlorophyll grains in 

 general. 



As to the occurrence of chlorophyll grains in the cell wall, 

 it is scarcely necessary to state that after very careful examina- 

 tion no such case was observed. Were I to attempt to explain 



I Schmitz, loc. cit. 



- Strasburger, loc. cit. 



» Pringslieim, ' Lichtwirkung und Chlorophyll fmipiifiii/ ISSl, p. 28. 



