188 Prof. P. Cohn on the Contractile Tissue of Plants. 



from what I think that I have seen in Oscillatoria princeps, 

 seems to take place in this family, not from tire conjugation of 

 its cells, but from the division of their contents into zoospores. 

 Much therefore remains to complete the history of this little 

 plant j and this, unfortunately, can only be obtained by watching 

 it long and narrowly in its proper habitat. 



XXI. — On the Contractile Tissue of Plants. 

 By Prof. Ferdinand Cohn*. 



Prop. Cohn commences his interesting essay by remarking that, 

 though modem discovery has rendered the boundary-line obscure 

 between the animal and the vegetable kingdoms, with respect 

 to the lowest organisms in each, yet the differential characters 

 between the higher forms of each subkingdom remain sufficiently 

 well marked. Nevertheless the phenomena of irritability and 

 of movement in parts of many higher plants bear a general re- 

 semblance to those presented by the tissues of the higher classes 

 of animals, though their active cause has been attributed to 

 mechanical forces in connexion with structural peculiarities. 

 Cohn addresses himself to the question whether these mechanical 

 hypotheses are sufficient and satisfactory, or whether the move- 

 ments and irritability of plants are not referable to structures 

 homologous with those concerned in their production and mani- 

 festation in animals. 



To solve this interesting question, Cohn appeals to observa- 

 tions made by himself and by a talented pupil, M. Krabsch, who 

 was induced by the Professor to repeat, in the first instance, the 

 old experiments of Treviranus and Morren on the irritability of 

 the filaments of Centaurea, as a prelude to new researches. 

 Kohlreuter established the fact of the irritability of the stamens 

 of Scolymus hispunicus, Serratula arvensis, Cynara sculymus, 

 and C. cardunculus, Onopordum arabicum, Centaurea moschata, 

 C. nigra, C. spinosa, and C. ragusina, Cineraria, Scabiosa glasti- 

 folia, S. benedicta, S. eriophora, and S. salmantica, Buphthalmium 

 maritimum, Cichorium intybus, and C. endivia, and Hieracium 

 sahaudum. Sowerby noticed the contractility of the anthers in 

 Centaurea Isnardi, and L. C. Trevii-anus made a particular study 

 of the movements of the filaments of Centaurea pidchella, whilst 

 Morren did the same for those of the Centaurea ruthenica. 

 Krabsch especially studied the movements of the anthers of 

 Centaurea macrocephala. 



* Translated, in abstract, from the 'Abhanfllungen tier Schlesischen 

 Gesellscliaft fiir vaterlandische Cultur,' Heft i. 1861, by J. T. Arlidge, M.B. 

 &A.B.(Lond.). 



