122 DROSERA ROTUNDIFOLIA. [Chap. VII. 



tcrval of 2 hrs. 50 m. all three tentacles were well inflected. Each 

 of these glands could have received only the jrijnf ^^ * grain, or 

 .00225 mg. A little drop of the same size and strength was also 

 applied to four other glands, and in 1 hr. two became inflected, 

 whilst the other two never moved. We here see, as in the case of 

 the half-minims placed on the discs, that the nitrate of ammonia 

 is more potent in causing inflection than the carbonate; for minute 

 drops of the latter salt of this strength produced no effect. I tried 

 minute drops of a still weaker solution of the nitrate, viz. one part 

 to 875 of water, on twenty-one glands, but no elfect whatever was 

 produced, except perhaps in one instance. 



Sixty-three leaves were immersed in solutions of various 

 strengths; other leaves being immersed at the same time in the 

 same pure water used in making the solutions. The results are 

 BO remarkable, though less so than with phosphate of ammonia, 

 that I must describe the experiments in detail, but I will give only 

 a few. In speaking of the successive periods when inflection oc- 

 curred, I always reckon from the time of first immersion. 



Having made some preliminary trials as a guide, five leaves 

 were placed in the same little vessel in thirty minims of a solution 

 of one part of the nitrate to 7875 of water (1 gr.to 18 oz.) ; and this 

 amount of fluid just suflTiced to cover them. After 2 hrs. 10 m. 

 three of the leaves were considerably inflected, and the other two 

 moderately. The glands of all became of so dark a red as almost 

 to deserve to be called black. After 8 hrs. four of the leaves had 

 all their tentacles more or less inflected; whilst the fifth, which I 

 then perceived to be an old leaf, had only thirty tentacles in- 

 flected. Next morning, after 23 hrs. 40 m., all the leaves were in 

 the same state, excepting that the old leaf had a few more ten- 

 tacles inflected. Five leaves which had been placed at the same 

 time in water were observed at the same intervals of time; after 

 2 hrs. 10 m. two of them had four, one had seven, one had ten, of 

 the long-headed marginal tentacles, and the fifth had four round- 

 headed tentacles, inflected. After 8 hrs. there was no change in 

 these leaves, and after 24 hrs. all the marginal tentacles had re- 

 expanded; but in one leaf, a dozen, and in a second leaf, half a 

 dozen, submarginal tentacles had become inflected. As the glands 

 of the five leaves in the solution were simultaneously darkened, no 

 doubt they had all absorbed a nearly equal amount of the salt: 

 and as -y^ of a grain was given to the five leaves together, each 

 got j^f-g of a grain (.045 mg.). I did not count the tentacles on 

 these leaves, which were moderately fine ones, but as the average 

 number on thirty-one leaves was 102, it would be safe to assume 

 that each bore on an average at least 160. If so, each of the dark- 

 ened glands could have received only rsT/^^nr of * grain of the 

 nitrate; and this caused the inflection of a great majority of the 

 tentacles. 



This plan of immersing several leaves in the same vessel is a 

 bad one, as it is impossible to feel sure that the more vigorous 

 leaves do not rob the weaker ones of their share of the salt. The 

 glands, moreover, must often touch one another or the sides of the 



