Chap. XIII.] SENSITIVENESS OF FILAMENTS. 239 



injured, being touched. After a day these three leaves 

 opened, and were fairly sensitive when the uninjured fila- 

 ments were touched. The sudden immersion of a leaf into 

 boiling water does not cause it to close. Judging from the 

 analogy of Drosera, the heat in these several cases was too 

 great and too suddenly applied. The surface of the blade is 

 very slightly sensitive; it may be freely and roughly 

 handled, without any movement being caused. A leaf was 

 scratched rather hard with a needle, but did not close; but 

 when the triangular space between the three filaments on 

 another leaf was similarly scratched, the lobes closed. They 

 always closed when the blade or midrib was deeply pricked 

 or cut. Inorganic bodies, even of large size, such as bits of 

 stone, glass, &c. or organic bodies not containing soluble 

 nitrogenous matter, such as bits of wood, cork, moss, or 

 bodies containing soluble nitrogenous matter, if perfectly 

 dry, such as bits of meat, albumen, gelatine, &c., may be 

 long left (and many were tried) on the lobes, and no move- 

 ment is excited. The result, however, is widely different, as 

 we shall presently see, if nitrogenous organic bodies which 

 are at all damp, are left on the lobes ; for these then close by 

 a slow and gradual movement, very different from that 

 caused by touching one of the sensitive filaments. The foot- 

 stalk is not in the least sensitive; a pin may be driven 

 through it, or it may be cut off, and no movement follows. 



The upper surface of the lobes, as already stated, is 

 thickly covered with small purplish, almost sessile glands.' 

 These have the power both of secretion and absorption; but, 

 unlike those of Drosera, they do not secrete until excited 

 by the absorption of nitrogenous matter. No other excite- 

 ment, as far as I have seen, produces this effect. Objects, 

 such as bits of wood, cork, moss, paper, stone, or glass, may 

 be left for a length of time on the surface of a leaf, and it 



[Gardiner has described these a central position; the protoplasm 



f lands In the ' Proceedings of the is much less granular than be- 



:. Society,' Tol. xxxvl. p. 180. fore, and contains a number of 



When at rest the gland-cells small vacuoles, so that the nu- 



show a grannlar protoplasm, con- cleus appears suspenf^'vl bv radl- 



talning In most cases a single atlng strands of protoplasu. in 



large vacuole; the nucleus Is situ- the centre of the cell, 



ated at the base of the cell. At Another change produced by 



the end of the secreting period the feeding the leaf is the ap- 



the following changes have oc- penrance, m the parenchyma, of 



curred. The nucleus seems to tufts of greenish yellow crystals 



diminish in size, It has assumed of unknown nature. F. D.] 



