BOTANY 



THE EXISTENCE OF MUSCLES IN PLANTS. 



A recent discovery, by M. Cohn, a German naturalist, of a contract- 

 ile tissue in plants, identical in properties with the muscular tissue 

 of animals, adds one more striking fact to the accumulated evidence 

 of identity between the vegetable and animal organizations. Well- 

 informed biologists, have for some time past been agreed on the impos- 

 sibility of drawing any absolute lines of demarcation between the two. 

 Instead of the marked opposition, which may still be read in popular 

 hand-books, thrown into the form of tabulated contrasts, we have 

 learned that the physical, chemical, and physiological characters, by 

 which the plant and animal were supposed to be separated, are une- 

 quivocally characteristic of both. It is impossible to deny that plants 

 have mobility, and some of them even locomotion. If we deny them 

 sensibility, it is on grounds which will equally exclude many classes 

 of animals ; and these grounds are anatomical. It is because we fail 

 to detect the mechanism of sensibility, that we endeavor to interpret 

 the phenomena as physical. It is because we associate sensibility and 

 contractility with peculiar nervous and muscular structures, that we 

 deny that certain phenomena observed in plants are what we should 

 consider them to be, if we could discover nerves and muscles. Take 

 the case of the sensitive plant Dioncea Afuscipula, or fly-trap. The 

 edges of its leaf are fringed with hairs, like an eyelid. On the in- 

 side of the leaf, six delicate hairs are arranged in such an order that it 

 would be difficult for an insect to traverse the leaf without touching 

 one of these hairs. No sooner is a hair touched, than the two sides of 

 the leaf suddenly close ; just as the two eyelids close when an insect, 

 or bit of dust, touches the sensitive surface. The leaf entraps the in- 

 sect the fringe of hairs on the edges interlacing like fingers of oppo- 

 site hands. If the insect be not speedily liberated, it is soon digested ; 

 as it would be in the stomach of an animal. It should be borne in 

 mind, that this " sensitiveness" is not the property of the whole leaf, 

 but is localized in the delicate hairs of the centre, precisely as sensi- 

 tiveness is localized in the nervous mechanism of animals. Now, com- 

 paring the phenomena observed in the plant with phenomena observed 

 in animals, it seems impossible to discern any marked distinction ; if 

 the eyelid's closing on an insect proves sensibility, if the arms of a 

 polyp closing on an insect proves sensibility, --then the closing of the 

 Dionosa proves it. But, the mechanism in the three cases is different. 

 In the eyelid, we find nerves and muscles ; in the polyp, we find mus- 

 cles, and no nerves; in the plant, neither nerves nor muscles. This 

 difficulty may be turned by considering all three cases as cases of con- 

 tractility only ; and the first, as contractility stimulated by sensibility. 



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