422 Scientific Proceedings^ Royal Dublin Society. 



are decomposed by bacteria and the products absorbed. It, therefore, seemed 

 probable that this water would be nearly neutral in reaction. Pitchers of 

 Sarracenia purpurea x Hort., in the Botanic Gardens, were examined, and an 

 old one was found to give a red colour with phenol red, denoting an alkaline 

 reaction. This, however, may have been due to chance contamination, such 

 as from a flake of whiting from the windows, for it was found that young 

 pitchers contained a clear colourless liquid of pH 5-0 to 5-2, as shown by 

 methyl red. Older pitchers of S. tolliana x Hort., varied from pH 6-0 to 6-8 

 when tested with brom thymol blue. It was subsequently discovered that 

 Wherry (1920) had tested this liquid in several species growing wild in the 

 swamps of the middle Atlantic States of the U.S.A. He found that the 

 liquid in the pitchers was usually " mediacid " or " subacid," namely, 

 pH 4 to 5 and pH 5 to 6 respectively. He attributed the acidity chiefly to 

 carbonic acid, but, though a saturated solution is in the mediacid region, it 

 would soon lose carbon dioxide, so another acid must be present. Where 

 the reaction was found to be between pH 6 and 8, he considers that calcium 

 bicarbonate had dropped into the upturned pitchers from leaves of other 

 plants which drew from alkaline water supplies. The Sarracenia plants 

 were always on acid hummocks when the soil around was alkaline. It has, 

 however, been shown by Hepburn (1918) that the unopened pitchers of 

 Sarracenia are sterile, and the liquid has a proteolytic enzyme ; in older 

 opened pitchers bacteria are symbiotic. It is, therefore, not at all surprising 

 that the contents of the pitchers should be acid when freshly opened, and it 

 may be that the alkaline reaction found in some, both by Wherry and the 

 writer, is not due to chance contamination, but to the products of digestion, 

 or to those of bacterial action. Bodine (1921) has proved that protozoan 

 cultures in hay or soil infusions change in time from an acid to an alkaline 

 reaction. Possibly the old pitchers alter owing to the development of 

 protozoa. This could be tested directly. 



An attempt was made to examine the liquid in pitchers of Nepenthes sp., 

 as this is known to have a digestive action, but unfortunately the pitchers 

 were dried up. Brosera hinata, Labill., was, however, plentiful, and the leaf- 

 hairs were well covered with the characteristic beads. On touching with a 

 glass rod and stirring with water on a watch-glass it was observed that it 

 was hard to get these mucilaginous droplets to mix. With brom thymol blue 

 and phenol red the reaction given was pH 7'0, but the former indicator 

 showed pH 6-4 when tested with the liquid round a dead fly. Thus it appears 

 that acid may be secreted only when the hair is stimulated, or it may have 

 come from the fly. 



