ON THE DH>X£A ML'SCIPULA. 



93 



<hc dionaeii muscipula, are soyicely pricked by an insect, 

 V. hcu the leaves told ui)ou themselves, and seize ihe itiseet. 

 The prickiiij^ occasions the discharge of a tluid, w iiich lioids 

 tlie leaves open by tilling- their vessels. Accordiiiyly vsiien 

 the plantis young, when the little glaadalous bodies are not 

 formed, when they are empty, or when tiie fluids do not 

 floA- abundantly, the leaves are folded upon themselves just 

 in the same manner as when they were pricked." 



However ingenious this theory may appear to others, it This thpory 

 does not seem to be juft, I havealready n lied Broussonet's '"'"^ J"'*^' 

 opinion with regard to tlie motions of the leaves oi' tl;e in- 

 digenous species of dicscra and think 1 have shown it to be 

 unsupported by fact. In the presvtnt instance ;; very simple 

 experiment vvdl be sufficient in my opinion, to allow us to 

 conclude, that the uiotiu.s of the leafy ajjpendages* of the 

 dionaia mu:st be owing- to some cthe • cmise, t.ian that jt'.ft 

 noticed, li we slightly touch the ii, side of oue of tlitse They contract 



armed lobes with a straw, or other soft body, m» as not toiu- "^^'*^" "" ^''■*^ 



, ' . ■ . can escupe. 



jure its structure in the least; the contraction almost in- 

 stantaneously commences, nor does it ceas, till the lobes 

 either come into contact with the straw, uv olhcr olfeturmg 

 body, or with each other, if the offending body be removed. 

 Now in this experiment the structure of the leaf is not in- 

 j_uredj no fluid escapes, but yet the cositiiiciion is complete; 

 hence it must be obvious, that the dis( n;irg ' of a fluid, which 

 could hold the leaves open by filling tiieir vessels, cuiijot be 

 the cause of the motiOn. 



Nearly at the end of the chapter on irritability Senne- f^-mr nrjuti'? 

 bier mentions some ideas, whieh C.impaietti entertained, ^^^^^^^f 

 lie t'xplains the motions of tiie seusitives by the air v.etsels 

 (trachees) of the petiole of the leal" &c. ; and suppoice, that 

 tliey are tilled with a ver elastic aqveo-aerial fluid. S^-n- 

 nebier says, that Campareiti believed lie could explain \n 

 the same manner the motions of the dior.cea, drusera, %!.<.:. 

 This hvpothesis seems to me so imnrobalde, so contrary to 

 analogy, and t>o inadrquale to explain the phenonjenon (alLowu 

 ing the vesi^^els did exist tilled with thiji aijneo-atrial H jid, 



* Ttii; lobe's of tht' die ii3;.i, vvhi'.-h contr.ict, :ue !mo>? iv a le "y I'-er:- 

 fligj (Sinitli\ iiilrvjduclion) thoui;!i sometimes 1 have called tliem t! e 

 leaf. " 



w hich 



