puted questii 



is that the actual growth depends upon and is the result of 

 such condition of cell wall. Owing to the pressure within, the 

 micella? of the wall are supposed to he separated from each 

 other until the extreme limit of elasticity is reached. In this 

 way place is made for the new particles of matter between the 

 old. 



This theory is known in botanical literature as theSachs-De 

 Vries theory as it was first suggested by Sachs and afterward 

 supported by De Vries. It is often referred to as the one sus- 

 tained by Naegeli, but a careful study of his works shows that 

 what he says upon this subject has reference to tissue tensions 

 for the most part, rather than to simple turgor. 



It is now claimed by Schwendener that there is no proof 

 whatever that the surface growth of the wall depends upon 

 turgor, and on the contrary, that there is considerable evidence 



that cells having an excess of turgor, are not growing at all, 

 while cells are found in a state of great activity whose turgor 

 is very small. One and one-half atmosphere is considered 

 about the medium for ordinary turgeseent cells. 



Again, in a certain kind of tissue found in stems of water 

 plants and others where large air spaces occur, growth of w T all 



