264 ALDROVANDA VESICULOSA. [Chap. XIV. 



points with broad bases, like the prickles on the stem of a 

 bramble or Kubus. As the rim is infolded, these points are 

 directed towards the midrib, and they appear at first as if 

 they were adapted to prevent the escape of prey; but this 

 can hardly be their chief function, for they are composed of 

 very delicate and highly flexible membrane, which can be 

 easily bent or quite doubled back without being cracked. 

 Nevertheless, the infolded rims, together with the points, 

 must somewhat interfere with the retrograde movement of 

 any small creature, as soon as the lobes begin to close. The 

 circumferential part of the leaf of Aldrovanda thus differs 

 greatly from that of Dionaja; nor can the points on t^e 

 rim be considered as homologous with the spikes round the 

 leaves of Dionaja, as these latter are prolongations of the 

 blade, and not mere epidermic productions. They appear 

 also to serve for a widely different purpose. 



On the concave gland-bearing portion of the lobes, and 

 especially on the midrib, there are numerous long, finely 

 pointed hairs, which, as Prof. Cohn remarks, there can be 

 little doubt are sensitive to a touch," and, when touched, 

 cause the leaf to close. They are formed of two rows of cells, 

 or, according to Cohn, sometimes of four, and do not include 

 any vasctdar tissue. They differ also from the six sensitive 

 filaments of Dionaa in being colourless, and in having a me- 

 dial as well as a basal articulation. No doubt it is owing 

 to these two articulations that, notwithstanding their 

 length, they escape being broken when the lobes close. 



The plants which I received during the early part of 

 October from Kew never opened their leaves, though sub- 

 jected to a high temperature. After examining the struc- 

 ture of some of them, I experimented on only two, as I hoped 

 that the plants would grow; and I now regret that I did not 

 sacrifice a greater number. 



A leaf was cut open along the midrib, and the glands 

 examined under a high power. It was then placed in a few 

 drops of an infusion of raw meat. After 3 hrs. 20 m. there 

 was no change, but when next examined after 23 hrs. 20 m., 

 the outer cells of the glands contained, instead of limpid 



[In a paper In the * Nnovo irritability rcaldes exclnslvely In 



Olornnle Rotnnico Itnllano,' vol. the contml jrlaudular region of 



vlll. 1S70. p. Ki, Mori KtatoH thnt the leaf. F. D.] 

 this la the caae, namely that the 



