GROWTH OF CELLS. ] 51 



In the disc of homogeneous mucilage lying in the 

 punctum vegetationis, new homogeneous mucilage is un- 

 ceasingly produced, so that it remains the same, although 

 its lower edge is continually being converted into gra- 

 nules, and thus a portion unceasingly given over into the 

 zone of granular mucilage. The lower part of the latter 

 passes continually over to the coloured zone, since in it 

 the formation of colouring matters, starch-granules, &c., 

 begins. The lower part of this continually applies itself 

 to the wall. In this manner the relations of the parti- 

 cular zones remain the same, although an unceasing pro- 

 cess of transformation is going on in them. 



The apical growth is thus connected with a production 

 of contents, which takes place at the apex of the cellular 

 branch . 



The membrane, which is of tolerably uniform thickness 

 in the lower part, becomes gradually thinner toward the 

 end of the cellular branch. Immediately over the disc of 

 homogeneous mucilage at the punctum vegetationis, the 

 membrane is very delicate, as in a young newly-formed 

 cell. It always remains so during the growth of the 

 branch. The gelatinous matter secreted by the disc of 

 mucilage is never appropriated to the thickening of the 

 membrane, but solely produces the expansion of it neces- 

 sitated by the growth of the apex. The membrane 

 expands likewise beneath the apex, and exhibits pheno- 

 mena there, similar to the universal growth of the cell 

 without apical growth ; at the same time it becomes 

 thickened by deposition of new layers. 



The membrane therefore exhibits different behaviour 

 at the apex and beneath this part. At the apex it is 

 continuously nourished, so to speak, or, as seems to me 

 a more correct expression of the fact, new membrane is 

 incessantly produced ; the process of formation of mem- 

 brane going on there remains the same so long as the 

 apical growth lasts in unlimited axes, therefore, it is 

 unlimited also. Beneath the apex, the membrane grows 



