126 DROSERA ROTUNDIFOLIA. [Cdap. VII. 



number in water. Notwithstanding the care taken and the 

 number of the trials made, when in the following year I 

 looked merely at the results, without reading over my ob- 

 servations, I again thought that there must have been some 

 error, and thirty-five fresh trials were made with the weakest 

 solution; but the results were as plainly marked as before. 

 Altogether, 106 carefully selected leaves were tried, both in 

 water and in solutions of the phosphate. Hence, after the 

 most anxious consideration, I can entertain no doubt of the 

 substantial accuracy of my results. 



Before giving my experiments, it may be well to premise that 

 crystallised phosphate of ammonia, such as I used, contains 35.33 

 per cent, of water of crystallisation; so that in all the following 

 trials the eflBcient elements formed only 64.07 per cent, of the salt 

 used. 



Extremely minute particles of the dry phosphate were placed 

 with the point of a needle on the secretion surrounding several 

 glands. These poured forth much secretion, were blackened, and 

 ultimately died; but the tentacles moved only slightly. The dose, 

 small as it was, evidently was too great, and the result was the 

 same as with particles of the carbonate of ammonia. 



Half-minims of a solution of one part to 437 of water were 

 placed on the discs of three leaves and acted most energetically, 

 causing the tentacles of one to be inflected in 15 m., and the blades 

 of all three to be much curved inwards in 2 hrs. 15 m. Similar 

 drops of a solution of one part to 1312 of water (1 gr. to 3 oz.) 

 were then placed on the discs of live leaves, so that each received 

 the yg'fj of a grain (.0225 mg.). After 8 hrs. the tentacles of four 

 of them were considerably inflected, and after 24 hra. the blades 

 of three. After 48 hrs. all five were almost fully re-expanded. I 

 may mention with respect to one of these leaves, that a drop of 

 water had been left during the previous 24 hrs. on its disc, but 

 produced no effect; and that this was hardly dry when the solu- 

 tion was added. 



Similar drops of a solution of one part to 1750 of water (1 gr. to 

 4 oz.) were next placed on the discs of six leaves; so that each re- 

 ceived ^Vrff o' * grain (.0109 nig.) ; after 8 hrs. three of them had 

 many tentacles and their blades inflected; two others had only a 

 few tentacles slightly inflected, and the sixth was not at all af- 

 fected. After 24 hrs. most of the leaves had a fev^ more tentacles 

 inflected, but one had begun to re-expand. We thus see that with 

 the more sensitive leaves the y^f^f of a grain, absorbed by the 

 central glands, is enough to make many of the exterior tentacles 

 and the blades bend, whereas the y^,r of a grain of the carbonate 

 similarly given produced no efl'ect; and j^ of a grain of the 

 nitrate was only just sulFicient to produce a well-marked effect. 



A minute drop, about equal to ^ of a minim, of a solution of 



