141 



1 



called eruption growth, the old membrane having burst, the 

 young shoot is built out of entirely new material. 



In a similar manner the growth of the cell wall in thickness 

 proceeds, by new layers added on to the old blue membrane. 

 As these new layers were added it was proven that foreign sub- 

 stances, like balls of dead protoplasm, could be enclosed in the 

 cellulose of the wall, and the author believes this to be the origin 



I the wall. 



Wiesner to be an essential part of 



The increase of the wall in surface, so far as it is not brought 

 about by the apical growth referred to above, is said to take 

 place by means of the stretching rendered possible by the influ- 

 ence of the protoplasm ; this extension, he says, is not as great, 

 however, as Naegeli affirms. 

 I The growth of the leaf-h'ke organs of Caulerpa takes place 



by new pieces of membrane, periodically breaking through the 

 upper edge of the old. Occasionally the point of vegetation was 

 seen to divide and two leaflets were formed, whose junction he 



, . supposed might be the place where the reproductive organs were 



formed. 



These observations were particularly well confirmed in the 

 nearly transparent structures o{ Bryopsis and Derhesia, while exact 



■ 



measurements show^ed that no supplementary increase of the 

 thickness of the blue zone had appeared, or, what is the same, 

 that no growth by intussusception had taken place at the same 

 time apposition was afoins- on. That this was not due to the iron 



iD^"*t. 



in the coloring matter was proven by comparison with uncolored 

 plants. 



The manner of origin of the new layers is represented by the 

 author in the following manner : The outer layer of protoplasm 

 becomes gradually more and more laden with particles of carbo- 

 hydrates, while the proteid matters retreat from the outside, until 

 at last, instead of the outer layer of protoplasm, a cellulose lamella 

 IS formed, which sits firmly upon the old wall. This is, indeed, 

 a process of intussusception, but it takes place in particles of living 

 protoplasm and not in those of a dead wall. 



Some examples are given of membranes which do not appear 

 to be a regular formation, but occurring now and then. Such 



