38 



BOTANY. 



division. The triangular apical cells of the growing stems 

 divide repeatedly in the manner shown in the diagram (Fig. 

 27). Here the cell ABC, bounded by the heavy black 



HI 



Fig. 27. Diagram to show mode of fission of the apical cell, as seen from above. 

 /, the cell -4, -B, C, divided by the partition 1 ; II, the game cell with a second par- 

 tition, 2 ; III, the same cell with a third partition, 3. 



lines, is first divided into two unequal portions by the parti- 

 tion 1, I. ; next the larger portion of the divided cell is again 



divided by the partition 2, II. ; 

 later, a'third partition (3, III.) 

 is formed, and so on. It is no- 

 ticeable that in this case the 

 partition always forms parallel 

 to the oldest wall of the divid- 

 ing cell. By continued growth 

 the apical cell retains, despite 

 its repeated divisions, its origi- 

 nal dimensions. 



50. The growing cells of the 

 stem of the English bean ( Vicia 

 faba) furnish a good illustration 

 of fission in the highest plants. 

 In this case, and in many 

 other, if not all, Dicotyledons, 

 the division takes place directly 

 Fig. 28.-Meri8tem-ceiis of the stem through the centrally placed 



of Vtdafaba, m procees oJ fission ; in ' J * 



the cells a, a, the process is in its nucleus (. .big. 28). Alter the 



earlier stage ; at b it is completed. X . ,. x 111 



300. After Pranti. formation ot the new wall each 



new nucleus moves away and occupies a position on the 

 opposite side of the cell from where it was formed (as at b 

 and k). 



