GROUPS OF APICAL CELLS. 



459 



one lobe of a leaf takes place by means of an apical cell, and that of another lobe 

 merely by so-called marginal cells, as in Fig. 292. From my way of looking at the 



relations of dependence of cell-division upon 



growth, however, such cases appear thoroughly 

 explicable. 



Flat structures, such as the shoots of 

 many Algae and Liverworts, and many leaves, 

 often show on a vertical section through the 

 flat tissue-body an arrangement of the cell- 

 walls which will be intelligible from Fig. 296. 

 A certain similarity of the cell-network with 

 that of a slender growing-point with an apical 

 cell impelled the earlier observers to assume 

 in such cases a special, type. They regarded 

 cells lying beside one another at the margin 

 as a series of neighbouring apical cells : this, 



from a purely formal point of view, is of course possible, but it contributes nothing 

 further to the explanation of the processes of growth. 



It must now suffice to have brought forward the few cases adduced from the 

 copious material obtained by observation : a further extension of these considerations 

 would without doubt presuppose more patience than may be expected from readers 

 who are not Botanists. 



Fig. 296. 



