804 PINGUKJULA VULGARIS. IChap. XVI. 



haps have l)oen expected from the sponge remaining damp and 

 supplying nitrogenous matter for a longer time. Tlie margins, with 

 the drops, became plainly incurved in 2 hrs. 17 m. The incurvation 

 subsequently increased somewhat, but after 24 hrs. had greatly 

 decreased. 



KxiH'riment 13. Drops of the same strong infusion of raw meat 

 were placed along the midrib of a young and rather deeply concave 

 leaf. The distance across the broadest part of the leaf, between the 

 naturally incurved edges, was .55 of an inch (13.97 mm.). In 3 hrs. 

 27 m. this distance was a trace less; in hrs. 27 m. it was exactly 

 .45 of an inch (11.43 mm.), and had therefore decreased by .1 of 

 an inch (2.54 mm.). After only 10 hrs. 37 m. the margin began 

 to re-expand, for the distance from edge to edge was now a trace 

 wider, and after 24 hrs. 20 m. was as great, within a hair's breadth, 

 as when the drops were first placed on the leaf. From this exi)eri- 

 ment we learn that the motor impulse can be transmitted to a 

 distance of .22 of an inch (5.590 mm.) in a transverse direction 

 from the midrib to both margins; but it would be safer to say .2 

 of an inch (.5.08 mm.), as the drops spread a little beyond the mid- 

 rib. The incurvation thus caused lasted for an unusually short 

 time. 



Experiment H. ^Three drops of a solution of one part of car- 

 bonate of ammonia to 218 of water (2 grs. to 1 oz.) were placed 

 on the margin of a leaf. These excited so much secretion that in 

 1 hr. 22 m. all three drops ran together; but although the leaf 

 was observed for 24 hrs., there was no trace of inflection. We 

 know that a rather strong solution of this salt, though it does not 

 injure the leaves of Drosera, paralyses their power of movement, 

 and I have no doubt, from [this and] the following case, that this 

 holds good with Pinguicula. 



Experiment 15. A row of drops of a solution of one part of 

 carbonate of ammonia to 875 of water (1 gr. to 2 oz.) was placed 

 on the margin of a leaf. In 1 hr. there was apparently some slight 

 incurvation, and this was well marked in 3 hrs. 30 m. After 24 

 hrs. the margin was almost completely re-expanded. 



Experiment 16. A row of large drops of a solution of one part 

 of phosphate of ammonia to 4375 of water (1 gr. to 10 oz.) was 

 placed along the margin of a leaf. No effect was produced, 

 and after 8 hrs. fresh drops were added along the same margin 

 without the least effect. We know that a solution of this 

 strength acts powerfully on Drosera, and it is just possible that 

 the solution was too strong. I regret that I did not try a weaker 

 solution. 



Experiment 17. As the pressure from bits of glass causes in- 

 cur\'ation, I scratche<l the margins of two leaves for some minutes 

 with a blunt needle, but no effect was produced. The surface of a 

 leaf beneath a drop of a strong infusion of raw meat was also 

 rubbe<l for 10 m. with the end of a bristle, so as to imitate the 

 struggles of a captured insect; but this part of the margin did 

 not bend sooner than the other parts with undisturbed drops of 

 the infusion. 



