38o 



A TEXTBOOK OF THEORETICAL BOTANY 



the internodal cell, but also join up with the series of cortical cells growing 

 from the next node. In this way each internodal cell becomes covered with 

 a layer of cells derived from both the upper and lower nodes. These cortical 

 filaments themselves exhibit apical growth and become differentiated into 

 nodes and internodes. The form of the cortications differs in the various 

 species, and is much more elaborate in some than in others. The laterals of 

 limited growth may become corticated as well as the main stem. 



The peripheral cells of the lower nodes also give rise to rhizoids with 

 apical growth. These rhizoids possess oblique septa, but are not differentiated 



APICAL CELL 

 OF BRANCH 



NODAL CELLS 



PERIPHERAL 

 CELL 



INTERNODAL 

 CELLS 



APICAL CELL ^^^om„ ,m A 

 )F STEM OOGONIUM f 



ANTHERIDIUM 



BRANCH 



INTERNODE 



BRANCH NODE 



CORTICAL CELLS 



DESCENDING 

 CORTEX 



STEM 

 INTERNODE 



ASCENDING 

 CORTEX 



STEM NODE 



Fig. 364. — Charo fragilis. A, Apex of axis, showing apical cell and differentiation of 

 branches. B, Branch axil on an older stem showing axillary bud and young repro- 

 ductive organs. {After Sachs.) 



into nodes and internodes. They branch by a complex process involving 

 the formation of a group of four lateral cells, from the lower pair of which 

 secondary rhizoids may be given oft. This process may be repeated. 



Finally, also from the basal node of the laterals, there may arise stipuloids, 

 which are unicellular outgrowths. Either a single row or a double row 

 may be formed. The cells are oval or pointed in shape, and the lower row 

 is directed downwards, while if a second row is present its cells will be 

 directed upwards over the lateral branches. The shape of the stipuloids is a 

 specific character. 



Cell Structure 



The cells of the nodes are relatively small, with dense, granular protoplasm 

 and a single nucleus. There are numerous small discoid chloroplasts, which 

 are disposed around the periphery of the cells. No pyrenoids are present. 

 The large internodal cells are sometimes multinucleate, and their nuclei 

 often possess large nucleoli and scanty chromatin. In these cells the 

 cytoplasm forms only a peripheral layer with a large central vacuole. The 



