62 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 
Fie. 14.— A, a plant of Chara, one of the Characee, 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 odgonium, og; J, 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 biciliate 
spermatozoid; D, a section through the node of a young leaf showing 
the young antheridium, an, below the odgonium, og; 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. 
