DESICCATION IN PHILODINA ROSEOLA. 377 



Pfeffer suggests that where death occurs as a result of drying 

 it may be due in part to the removal of the last traces of absorbed 

 or combined water. He says: "Since full turgor is restored in 

 mosses and other plants immediately after moistening them, it is 

 evident that the osmotic materials remain as solids in the central 

 vacuole. Evidently, therefore, the protoplasm is not injured by 

 the concentrated cell sap. If, however, the latter is responsible 

 for the death of certain plants on drying, we have revealed to 

 us in such cases the immediate cause of the fatal action of desic- 

 cation. It is, however, hardly likely that the death of plants 

 killed by the removal of more or less of the imbibed water, as 

 well as that of those only killed by the removal of the last traces 

 of absorbed or even combined water, is alike produced in the 

 same way." 



I believe that the work of McDougal, Long and Brown, 

 mentioned in the next paragraph shows that plants may have 

 their cell sap concentrated in the fashion described by Pfeffer 

 and still recover from the process. My own observations upon 

 Philodina lead me to think that death at the time of drying 

 cannot be attributed to such a cause but rather to a lack of a 

 complete adaptive rearrangement of cytoplasmic and nuclear 

 material. 



Among the botanists the subject of desiccation is now being 

 studied by McDougal and his associates at the Desert Laboratory 

 at Tucson, Ariz. A recent paper from that laboratory deals 

 with cytological phenomena in the desiccation of Echinocactus . 

 J. G. Brown, who did the cytological part of the work, examined 

 four kinds of cells in the tissues of Echinocactus wislizeni, viz., 

 integument, palisade, outer cortex and deep cortex. Starting 

 with a description of these cells in sections of a plant grown 

 under normal conditions he compares similar cells from sections 

 of (i) a plant which had been desiccated six years; (2) one which 

 had been desiccated ten months; and (3) one which had been 

 desiccated forty-two months and then allowed to grow under 

 normal conditions for twenty-two months. 



In the palisade cells the results of desiccation were most 

 apparent. These cells are rectangular in section, having a peri- 

 pheral layer of protoplasm embedded in which are the nucleus 

 and plastids. A corresponding cell from a plant desiccated six 



