Prof. F. Cohu on the Contractile Tissue of Plants. 201 



33. The following is a summary of the foregoing researches 

 on the stamens of Centaurea : — 



1. The stamens shorten themselves, on mechanical contact, 

 instantaneously throughout their length. This holds true, also, 

 when only one point is touched, and also of all parts of those 

 organs. The contraction amounts to one-seventh of their length, 

 and, in certain conditions, to one-fourth. Simultaneously with 

 their contraction, the stamens also become thicker. 



2. After the shortening has attained its maximum, the fila- 

 ments begin to extend themselves, and to acquire a curved con- 

 dition similar to what occurs in an irritated muscle. After the 

 lapse of ten minutes, they regain their former length. 



3. Other excitants, especially a current of electricity trans- 

 mitted through the filaments, produce immediate contraction. 



4. The irritability of the filaments vanishes spontaneously 

 after a while — in the living flower, about the time when the 

 segments of the style expand themselves and the stigma is in a 

 condition for fertilization. But, coeval with these changes, the 

 stamens become progressively shorter, and, when completely de- 

 prived of their irritability, are only one-half the length they were 

 when in the full possession of that property. 



3. This persistent shortening, which must not be confounded 

 with contraction resulting transiently from previous irritation, is 

 a symptom of death, not a hygroscopic phenomenon. At the 

 same time it is induced much more rapidly when the instability 

 of the stamens is destroyed by the vapour of ether, by immersion 

 in water, or by strong electric discharges. 



6. The shortening in death is chiefly an effect of elasticity, 

 which, in the irritable filaments, is subordinate to an expansive 

 power; but, in the dead or withered state, the antagonism of 

 this latter is withdrawn, and the filaments become shortened to 

 one-half their length, and are highly elastic, like threads of india- 

 rubber. 



7. The property of shortening resides in the parenchyma of 

 the stamens, which presents no especial difi'erence from ordinary 

 cell-structure ; and the vascular bundle is at least passive during 

 contraction. 



8. The foregoing, along with other similar researches, go to 

 demonstrate that the cell-tissue of the filaments of Centaurea 

 possesses irritability (in the sense used by Haller) and likewise 

 an innate motor power, both these properties resembling in all 

 essential points their like as found in the contractile and irri- 

 table parts of animals. This analogy does not imply the exist- 

 ence of muscles and associated nerves, as found in the higher 

 animals, where a physiological differentiation of tissues prevails 

 in order to qualify for the performance of functions of the highest 



Ann. i^ Mag, N. Hist. Ser.3. Fo/. xi. 14 



