BULLETIN 



OF THE 



s 



TORREY BOTANICAL CLUB. 



Vol- IX.l New York, April; 1882. [No. 4. 



Development of the Cortex in Chara. 



Illustrated by a Series of American Species. 



By T. F. Allen, 



(Plates xv-xxii,) 



A classification of the species of Chara based upon a correct and 

 thorough knowledge of their morphological characteristics was first 

 attempted by the late Prof. A. Braun, who so arranged the genera 

 and species of the whole order Characeae, that we are able to trace 

 a gradual development from the simplest dioecious Nifella^ with uni- 

 cellular stems and leaves, to the most completely developed Chara 

 {C, fragilis, Desv.). The formation of *' nodes " and a complete de- 

 velopment of the node-bract and fruit-bearing leaf maybe already 

 seen in the simplest Chara ; but the genus is still further elevated by 

 the growth of a cortical series of cells, which may be traced from the 

 rudimentary cells of the leaf-node to a perfect evolution. 



The development of ** stipules " (traces of which begin to appear 

 in the most highly organized Nitella) has been used by Prof. Braun 

 to mark the three general divisions of the genus Chara, and the 

 character of the cortication serves to mark sub-divisions. Both stip- 

 ular and cortical cells spring from the nodal cells, and a considera- 

 tion of their character must be preceded by an inquiry into the nature 

 of a node. 



The stem of a characeous plant grows through the formation of 

 cells, by a process of sub-division of the apical growing cell. In 

 Plate XV, Fi^ la^ a represents the growing apical cell; n, a cell vyhich 

 has itself sub-3ivided and is destined to be the node ; and /, an inter- 

 nodal cell which does does not sub-divide, but which is destined to 

 elongate indefinitely. The next figure (Fig. i^) illustrates a developed 

 stem, in which the inter-nodal cells /, / have extended, while the nodal 

 cell n has sub-divided, but has not elongated. 



From these nodal cells develop, in various ways,^ all organs— leaf, 

 bract and new shoots ; antheridia and sporangia ; stipules and 

 cortex. 



Since, in this paper, we have to deal with the development of the 

 cortex of the stem only, we may consider first a node of the stem with 

 a basilar node of a leaf. 



*' A primary nodal-cell of the stem divides, soon after its origin, 

 into two secondary cells by means of a vertical septum through its 

 diameter ; in each of these half-cells a semi-circle of peripheral cells 

 forms by a farther eccentric, vertical fissation in such manner that a 

 new fissation occurs alternately on one or the other side of the semi- 

 circle. Both semi-circles begin on the same side of the node, pro- 

 gress toward each other, and, when at last they close together, form 

 a complete circle of cells enclosing the two central cells, which, as 

 remnants of the original halving-cell, form the nodal cells in the 



