24O PROCESS OF DEVELOPEMENT. CHAP. IV, 



describes it, gave no countenance whatever to the 



doctrine of a circulation of juices. 



According But the doctrine, as it appears, has been again 

 Cort C i,Tn g d revived, and has met with the support of some 



of the most distinguished of modern phytologists. 



now 



Hedwig is said to have declared himself to be of 

 opinion that plants have a circulation of fluids si- 

 milar to that of animals. But as I am not ac- 

 quainted with the arguments on which his opinion 

 is founded, I can say nothing with regard to them. 

 Corti is said to have discovered a species of circu- 

 lation in the stern of the Chara, confined as I 

 believe, within the limits of the internodia. But 

 perhaps it was nothing more tban a sort of vibra- 

 tory motion of the contained fluids, similar to that 

 which I observed in the peduncle of the Mar- 

 chantia, as related in the Analysis of the Internal 

 Structure. Willdenow has also introduced the sub- 

 ject, and defended the doctrine, in his Principles of 

 Botany ; * but only by saying he believes a circu- 

 lation to exist, and that it is impossible for the 

 leafless tree to resist the cold if there be not a circu- 

 lation of fluids ; which, as it is no argument, merits 

 no particular reply. 



According But as Mr. Knight has given his reasons sorne- 



to Knight, w j )at more i n detail, we will also be somewhat more 



particular in endeavouring to ascertain their value. 



The experiments by which Mr. Knight accounts for 



the conversion of the alburnum into wood have 



been already stated in detail. But he is of opinion 



* English Trans, p. 285. 



