Rttrospective Criticism, 757 



irritability of the glandular hairs on the viscose leaf of this 

 plant, and justly ridicules the newspaper nonsense about feed- 

 ing its voraciousness with beef. I have observed this, as well 

 as Drosera anglica and D. longifcMia (which are plentiful in 

 our neighbourhood), and can safely affirm that it has as de- 

 cided an irritabihty as the far-famed Dionae^« Muscipula. It 

 is quite possible that the glutinous matter on the tips of these 

 hairs, which has gained the plant its classical appellation of 

 sundew, may be principally instrumental in detaining the ven- 

 turous insect ; and that this may be of a poisonous quality, 

 destructive especially of insect life; but such a supposition 

 will not, alone, account for the circumstance, that when an 

 unfortunate fly has got into the centre of a leaf of Drosera, 

 every hair turns inward, and remains curled in till the prisoner 

 is not only dead^ but entirely consumed, and then the disc, 

 which before was extremely contracted and cone-like, expands 

 to its fullest breadth, and the hairs again become erect. No 

 other hypothesis, I think, will account for these phenomena, 

 which I have witnessed many times, except the irritable power 

 of the plant. The leaf of Drosera anglica, when a fly settles 

 on it, becomes rolled up circinally, and remains in this form 

 till the animal is dead. — William Thomson. Manchester, 

 June 14. 1832. 



Drosera rotundifblia, — In support of my ascribing (Vol. IV. 

 p. 135.) a faculty of irritability to the glandular hairs on the 

 leaves of Drosera rotundifcViia, I have the remarks of Mr. 

 Gordon (Vol. V. p. 26.) ; and Smith, in his English Flora, 

 vol. ii. p. 122., — " these hairs,'' says Smith, "have been 

 thought irritable, so as to contract when touched, imprisoning 

 insects, somewhat in the manner of the American Dionae^a 

 Muscipula L., a plant allied to Drosera." The Encyclopcedia 

 of Plants, p. 233., states, that the leaf hairs of Drosera rotun- 

 difolia are very irritable. I confess I have never been able, 

 except very slightly, to excite the contractility questioned, but 

 this might arise rather from an improper application of the 

 stimulus than from absence of the faculty ; but when I pressed 

 the centre of a leaf with any substance, there was, in certain 

 cases, a manifest inclination of the surrounding hairs to close 

 over it, although I met with no decisive instances. 1 must 

 mention, that in no case did I find any object upon the leaf; 

 but observed that the hairs were curved inwards, so as to form 

 with their globules a group over the centre of the leaf. On 

 old leaves the centre is generally bare of glandular hairs, and 

 the leaf perfectly flat, while the outer hairs alone remain, are 

 unbent, and without any liquid in the minute globules with 

 which they are tipped ; as if by some strong excitement their 



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