EVOLUTION OF PLANTS 



the cell, and the cells have long been favorite subjects 

 for demonstrating this phenomenon. The original 

 nucleus of these elongated cells becomes early divided 

 into many, but these secondary nuclei are not formed 



FIG. 14. A, a plant of Chara, one of the Characeae, showing the division 

 of the stem into nodes and internodes, and the method of branching ; 

 B, part of a leaf with an antheridium an, and oogonium, oy ; I, leaflets 

 at the node of the leaf; C, a group of filaments from the interior 

 of the antheridium ; each cell of the long filament contains a hiciliate 

 spermatozoid ; D, a section through the node of a young leaf showing 

 the young antheridium, an, below the oogonium, oy ; E, a single 

 spermatozoid ; F, a longitudinal section of the stem-apex, showing the 

 apical cell, v, from the division of which all the parts of the plant 

 arise ; x, the nodes, y, the internodes. 



by the ordinary nuclear division, or karyokinesis, but 

 result from a direct constriction, or fragmentation of 

 the primary nucleus, a phenomenon which has also 

 been met with in the elongated cells of the stems of 

 some flowering plants. 



