48 DROSERA ROTUNDIPOLU, [Chap. III. 



It is an important fact that when an organic or inorganic 

 object is placed on the glands of the disc, and the exterior 

 tentacles are thus caused to bend inwards, not only is the 

 secretion from the glands of the latter increased in quantity 

 and rendered acid, but the contents of the cells of their 

 pedicels become aggregated. The process always commences 

 in the glands, although these have not as yet touched any 

 object. Some force or influence must, therefore, be trans- 

 mitted from the central glands to the exterior tentacles, first 

 to near their bases causing this part to bend, and next to the 

 glands causing them to secrete more copiously. After a 

 short time the glands, thus indirectly excited, transmit or 

 reflect some influence down their own pedicels, induc^g 

 aggregation in cell beneath cell to their bases. 



It seems at first sight a probable view that aggregation is 

 due to the glands being excited to secrete more copiously, so 

 that sufficient fluid is not left in their cells, and in the cells 

 of the pedicels, to hold the protoplasm in solution. In favour 

 of this view is the fact that aggregation follows the inflection 

 of the tentacles, and during the movement the glands gener- 

 ally, or, as I believe, always, secrete more copiously than 

 they did before. Again, during the re-expansion of the -ten- 

 tacles, the glands secrete less freely, or quite cease to secrete, 

 and the aggregated masses of protoplasm are then redissolved. 

 Moreover, when leaves are immersed in dense vegetable solu- 

 tions, or in glycerine, the fluid within the gland-cells passes 

 outwards, and there is aggregation; and when the leaves are 

 afterwards immersed in water, or in an innocuous fluid of less 

 specific gravity than water, the protoplasm is redissolved, and 

 this, no doubt, is due to endosmose. 



Opposed to this view, that aggregation is caused by the 

 outward passage of fluid from the cells, are the following 

 facts. There seems no close relation between the degree of 

 increased secretion and that of aggregation. Thus a particle 

 of sugar added to the secretion round a gland causes a much 

 greater increase of secretion, and much less aggregation, 

 than does a particle of carbonate of ammonia given in the 

 same manner. It does not appear probable that pure water 

 would cause much exosmose, and yet aggregation often fol- 

 lows from an immersion in water of between 16 hrs. and 

 24 hrs., and always after from 24 hrs. to 48 hrs. Still less 



