8 DROSERA EOTUNDIPOLIA. [Chap. I. 



hours. The difference in the time required depends on many 

 circumstances; namely, on the size of the object and on its 

 nature, that is, whether it contains soluble matter of the 

 proper kind; on the vigour and age of the leaf; whether it 

 has lately been in action; and, according to Nitschke,* on 

 the temperature of the day, as likewise seemed to me to be the 

 case. A living insect -is a more eflBcient object than a dead 

 one, as in struggling it presses against the glands of many 

 tentacles. An insect, such as a fly, with thin integuments, 

 through which animal matter in solution can readily pass 

 into the surrounding dense secretion, is more efficient in 

 causing prolonged inflection than an insect with a thick coat, 

 such as a beetle. The inflection of the tentacles takes place 

 indifferently in the light and darkness; and the plant is not 

 subject to any nocturnal movements of so-called sleep. 



If the glands en the disc are repeatedly touched or brushed, 

 although no object is left on them, the marginal tentacles 

 curve inwards. So again, if drops of various fluids, for in- 

 stance of saliva or of a solution of any salt of ammonia, are 

 placed on the central glands, the same result quickly follows, 

 sometimes in under half an hour. 



The tentacles in the act of inflection sweep through a wide 

 space; thus a marginal tentacle, extended in the same plane 

 with the blade, moves through an angle of 180 ; and I have 

 seen the much reflected tentacles of a leaf which stood up- 

 right move through an angle of not less than 270". The bend- 

 ing part is almost confined to a short space near the base; 

 but a rather larger portion of the elongated exterior tentacles 

 becomes slightly incurved, the distal half in all cases re- 

 maining straight. The short tentacles in the centre of the 

 disc, when directly excited, do not become inflected; but they 

 are capable of inflection if excited by a motor impulse received 

 from other glands at a distance. Thus, if a leaf is immersed 

 in an infusion of raw meat, or in a weak solution of ammonia 

 (if the solution is at all strong, the leaf is paralysed), all the 

 exterior tentacles bend inwards (see Fig. 4), excepting those 

 near the centre, which remain upright; but these bend to- 

 wards any exciting object placed on one side of the disc, as 

 shown in Fig. 5. The glands in Fig. 4 may be seen to form a 

 dark ring round the centre; and this follows from the ex- 



Bot. ZeltUDg,' 1800. p. 240. 



