92 RISE OF THE SPRING SAP. 



plums, &c., passes, on contact with the air, into a 

 The plant state of progressive change. The fungi which have 

 fungi and been observed on the potato-plants, and the putre- 



putrefaction 



follow. faction of the tubers, are not the signs of a disease, 



but the consequences of the death of the plant. 

 observa- Among the most important of the experiments 

 HALES on made by HALES we must reckon undoubtedly those 



the rise of J . J 



the spring on the rise of the spring sap in perennial plants. 

 enniai His observations have been entirely confirmed by all 



those who since his time have studied the subject ; 



but, in my opinion, without our having approached 



one step nearer to the cause of the phenomena. 

 The most recent experiments on this subject by 



E. BRUCKE, leave no doubt in regard to the actual 



state of our knowledge. 

 views of According to DUTROCHET, it is the extremities 



of the radical fibres, called by DE CANDOLLE 



spongioles, which effect the rise of the spring sap ; 

 and he believes (L'agent immediat du mouvement 

 vital, Paris, 1826) that the force, with which the 

 sap is driven upwards, acts from the root. DU- 

 TROCHET cut off a piece of a vine stem, two metres 

 long ; and he saw that the sap flowed steadily from 

 the shortened stem in connection with the root. 

 When he had again cut it off close to the ground, he 

 observed that the portion in the ground continued 

 to pour forth sap from the whole cut surface. He 

 pursued the experiment, going deeper every time, 

 He places anc ^ ne a l wa ys found, that the sap flowed from the 

 fhespo C n- in P art left in the ground, till at last he came to the 



