CHAP. VII. PHOSPHATE OF AMMONIA. 153 



88 m. ; a third, eighteen inflected, after 1 hr. ; and a fourth, 

 ten inflected, after 35 m. The four other leaves were not in 

 the least affected. Of the eight corresponding leaves in water, 

 one had, after 2 hrs. 10 m., nine tentacles, and four others from 

 one to four long-headed tentacles, inflected ; the remaining three 

 being unaffected. Hence, the ^Vo of a grain given to a sensi- 

 tive leaf during warm weather perhaps produces a slight effect; 

 but we must bear in mind that occasionally water causes as 

 great an amount of inflection as occurred in this last ex- 

 periment. 



Summary of the Results with Nitrate of Ammonia. 

 The glands of the disc, when excited by a half-minim 

 drop ('0296 ml.), containing -^Vo of a grain of the 

 nitrate ('027 nig.), transmit a motor impulse to the 

 exterior tentacles, causing them to bend inwards. A 

 minute drop, containing -jnnhro f a grain ('00225 mg.), 

 if held for a few seconds in contact with a gland, 

 causes the tentacle bearing this gland to be inflected 

 If a leaf is left immersed for a few hours, and some- 

 times for only a few minutes, in a solution of such 

 strength that each gland can absorb only the 



~t> 9 1 a o o 



of a grain (-0000937 nig.), this small amount is 

 enough to excite each tentacle into movement, and 

 it becomes closely inflected. 



PHOSPHATE OF AMMONIA. 



This salt is more powerful than the nitrate, even 

 in a greater degree than the nitrate is more powerful 

 than the carbonate. This is shown by weaker solu- 

 tions of the phosphate acting when dropped on the 

 discs, or applied to the glands of the exterior ten- 

 tacles, or when leaves are immersed. The difference 

 in the power of these three salts, as tried in three 

 different ways, supports the results presently to be 



