6S DROSERA ROTUNDIFOLIA. [Chap. V. 



on the leavea, all four had almost re-expanded. They were then 

 given little bits of meat, and tlu-sc acted more i)owerfuny than the 

 solution. One part of isinglass was next dissolved in 437 of water: 

 the fluid thus formed was so thin that it could not be distinguished 

 from pure water. The usual-sized drops were placed on seven 

 leaves, each of which thus received 7^0 of a grain (.0295 mg.). 

 'I'luee of them were observed for 41 hrs., but were in no way af- 

 fected; the fourth and fifth had two or three of their exterior ten- 

 tacles inflected after 18 hrs.; the sixth had a few more; and the 

 seventh had in addition the edge of the leaf just perceptibly curved 

 inwards. The tentacles* of the four latter leaves began to re-expand 

 after an additional interval of only 8 hrs. Hence the -^ of a 

 grain of isinglass is suilicicnt to affect very slightly the more sen- 

 sitive or active leaves. On one of the leaves, which had not been 

 acted on by the weak solution, and on another, which had only 

 two of its tentacles inflected, drops of the solution as thick as 

 milk were placed; and next morning, after an interval of 16 hrs., 

 both were found with all their tentacles strongly inflected. 



Altogether I experimented on sixty-four leaves with the 

 above nitrogenous fluids, the five leaves tried only with the 

 extremely weak solution of isinglass not being included, nor 

 the numerous trials subsequently made, of which no exact 

 account was kept. Of these sixty-four leaves, sixty-three 

 had their tentacles and often their blades well inflected. 

 The one which failed was probably too old and torpid. But 

 to obtain so large a proportion of successful cases, care must 

 be taken to select young and active leaves. Leaves in this 

 condition were chosen with equal care for the sixty-one trials 

 with non-nitrogenous fluids (water not included) ; and we 

 have seen that not one of these was in the least affected. 

 We may therefore safely conclude that in the sixty-four ex- 

 periments with nitrogenous fluids the inflection of the ex- 

 terior tentacles was due to the absorption of nitrogenous 

 matter by the glands of the tentacles on the disc. 



Some of the leaves which were not affected by the non- 

 nitrogenous fluids were, as above stated, immediately after- 

 wards tested with bits of meat, and were thus proved to be 

 in an active condition. But in addition to these trials, 

 twenty-three of the leaves, with drops of gum, syrup, or 

 starch, still lying on their discs, which had produced no 

 effect in the course of between 24 hrs. and 48 hrs., were then 

 tested with drops of milk, urine, or albumen. Of the twenty- 

 three leaves thus treated, seventeen had their tentacles, and 



