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BOTANY 



upward, into an upper cell (x), from which the node arises, and a 

 lower internodal cell (y), which undergoes no further division, but 

 finally increases enormously in size. In many species of Chara 

 the long internodal cell is covered by a cortex, or rind, but in the 

 other genera the cortex is very incomplete, or quite wanting. 



All of the lateral organs are outgrowths of the nodes. The pri- 

 mary nodal cell in the stem of Chara (Fig. 90, B, C) divides first by 

 a vertical wall into equal parts. From these two cells, by repeated 

 division, a series of peripheral cells is cut off, so that a transverse 

 section of the young node shows two central cells and a circle of 

 peripheral cells of different ages. Each peripheral cell becomes the 



G 



FIG. 90. Plant of Chara frag His (natural size). B, longitudinal section of stem- 

 apex of Chara sp. ; v, apical cell; x, y, node and internode of youngest segment; 

 I, a leaf (X 200). C, cross-section of a young node. D, cross-section of older 

 internode, showing cortex (x 50). E, young cortical lobes (X200). F, older 

 cortex of C.fragilis. G, longitudinal section of young leaf. 



apical cell for a lateral branch or leaf, and divides very much like 

 the apical cell of the main shoot, except that the divisions in the 

 nodes are somewhat fewer, and the apical cell, after a certain num- 

 ber of segments have been cut off, ceases to divide further, and 

 elongates to form the pointed terminal cell of the leaf (Fig. 90, G). 



From the nodes of the leaves leaflets are developed, which may, 

 in some cases, be replaced by the reproductive organs. 



Cortex. In most species of Chara the basal node of each leaf 

 gives rise to two peculiar branches, which grow one upward and one 

 down, closely appressed to the outer surface of the internodes, which 

 they completely conceal. The growth of these branches, or corti- 



