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 fig. 296. 



as a series of neighbouring apical cells : this, 



from a purely formal point of view, is of course possible, but it contributes nothino- 

 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. 



