CHAP. VII. PHOSPHATE OF AMMONIA. ]57 



fleeted ; and one was not at all acted on. By an accident only 

 fifteen, instead of eighteen, leaves were immersed at the same 

 time in water ; these were observed for 24 hrs. ; one had six, 

 another four, and a third two, of their outer tentacles inflected ; 

 the remainder being quite unaffected. 



The next experiment was tried under very favourable circum- 

 stances, fort he day (July 8) was very warm, and I happened 

 to have unusually fine leaves. Five were immersed as before in 

 a solution of one part to 131,250 of water (1 gr. to 300 oz.), sc 

 that each received ^o of a grain, or '0135 mg. After an 

 immersion of 25 m. all five leaves were much inflected. After 

 1 hr. 25 m. one leaf had all but eight tentacles inflected; the 

 second, all but three ; the third, all but five ; the fourth, all but 

 twenty-three; the fifth, on the other hand, never had more 

 than twenty-four inflected. Of the corresponding five leaves in 

 water, one had seven, a second two, a third ten, a fourth one, 

 and a fifth none inflected. Let it be observed what a contrast 

 is presented between these latter leaves and those in the solu- 

 tion. I counted the glands on the second leaf in the solution, 

 and the number was 217 ; assigning that the three tentacles 

 which did not become inflected absorbed nothing, we find 

 that each of the 214 remaining glands could have absorbed 

 onl y 1027200 of a grain, or -0000631 mg. The third leaf bore 

 236 glands, and subtracting the five which did not become in- 

 flected, each of the remaining 231 glands could have absorbed 

 onlv iiossoo f a 8 Tam ( or "0000584 mg.), and this amount 

 sufficed .to cause the tentacles to bend. 



Twelve leaves were tried as before in a solution of one part to 

 175,000 of water (1 gr. to 400 oz.), so that ea-ch leaf received -g^Vo 

 of a grain ('0101 mg.). My plants were not at the time in 

 a good state, and many of the leaves were young and pale. 

 Nevertheless, two of them had all their tentacles, except three 

 or four, closely inflected in under 1 hr. Seven were con- 

 siderably affected, some within 1 hr., and others not until 3 hrs., 

 4 hrs. 30 m., and 8 hrs. had elapsed; and this slow action 

 may be attributed to the leaves being young and pale. Of 

 these nine leaves, four had their blades well inflected, and a 

 fifth slightly so. The three remaining leaves were not affected. 

 With respect to the twelve corresponding leaves in water, not 

 one had its blade inflected ; after from 1 to 2 hrs. one had 

 thirteen of its outer tentacles inflected; a second six, and four 

 others either one or two inflected. After 8 hrs. the outer 

 tentacles did not become more inflected ; whereas this occurred 

 with the leaves in the solution. I record in my notes that 



