64 



PLANT MORPHOLOGY 



arise from the nodes and form a one-layered cortex. Half of the cortical 

 cells are derived from the node below and half from the node above, the 

 two halves meeting in a zigzag line midway between the nodes. In 

 Niiella the Internodes remain uncovered. 



Reproduction. No spores are produced in the Charophyceae. The 

 nodes of the branches of limited growth bear unicellular branches and the 

 sex organs, which are the most complex of all the algae. Most species are 



Fig. 51. Chara. A, upper portion of plant, showing branches of Hmited and unlimited 

 growth, natural size; B, median longitudinal section through the stem tip, showing promi- 

 nent apical cell and alternating nodes and internodes derived from it, X200. The large 

 internodal cell below is being ensheathed by a layer of cortical cells arising from adjacent 

 nodes. 



monoecious, an antheridium lying below an oogonium at the same node 

 (Fig. 52). The antheridium is a stalked globular body that is brilliant 

 red or yellow. It develops from a single initial cell that at first divides in 

 three planes to produce octants. Each octant then undergoes two peri- 

 clinal divisions to form an outer, a middle, and an inner cell. A jacket 

 of eight triangular plate-like cells, called shields, is derived from the outer 

 cells. The rapid enlargement of the shields results in the formation of a 

 cavity within the antheridium. Projecting inward from the center of 

 each shield is an elongated cell, the manubrium, that bears a rounded 

 terminal cell, called a primary capitulum, which often divides in two. 

 The manubria and primary capitula are derived from the middle and 



