chap, i Processes of Absorption of Water 249 



plants. The view of a selective power of the roots, based upon 

 the older work of De Saussure, remained a difficulty and met 

 with no adequate treatment. The work of Dutrochet, like 

 that of most of the writers of his time, though displacing 

 the old vitalistic theories, led him to too mechanical a con- 

 ception, which only found correction during the period 

 from i860 onwards, when the doctrine of the independent 

 life and vital functions of protoplasm gradually impressed 

 itself upon the minds of physiologists. 



At the commencement of our period another obstacle to 

 progress was in existence, an error in the interpretation 

 of structure, which had laid hold of botanical opinion, and 

 which died hard. This was the spongiole theory of the 

 root, associated with the name of De Candolle. According 

 to the latter, the roots of terrestrial plants are furnished 

 with peculiar spongy absorbent organs, which are developed 

 at their apices. They are capable of active contraction, by 

 means of which they force into the root such water as, 

 by virtue of their hygroscopic qualities and by capillarity, 

 they have been able to accumulate in their substance from 

 outside. It is difficult to reconcile this view of structure 

 with the hypothesis of Dutrochet, but it held its own with 

 great tenacity, though anatomical researches clearly dis- 

 proved it. 



The position as left by Dutrochet was practically un- 

 changed in i860. Very soon afterwards research was again 

 directed to these fundamental questions, and many exhaus- 

 tive investigations were made upon the whole subject during 

 the rest of the period under review ; different sections of it 

 fell into the hands of different botanists and were made 

 the subjects of separate inquiries by the most eminent 

 investigators, and of discussion by the ablest critics and 

 thinkers of the time. 



These researches into different aspects of the problem 

 were not consecutive, but overlapped considerably in 



