28 BRITISH CHAROPHYTA. 



to the bract-cells produced direct from the periphery 

 of the branchlet-node, a pair of similar organs spring 

 from the node at the base of the oogonium ; these are 

 styled bracteoles. The function of the bract-cells is 

 evidently similar to that of the bracts of flowering 

 plants, i. e., the protection of the young organs of 

 reproduction. The branchlets of many of the Charm 

 are covered with a cortex, which will be described 

 later. 



The general construction and development of the 

 branchlets of a corticate Ghara are shown in Fig. 5 be., 

 p. 24, and the cell-divisions of one of the nodes in 

 Fig. 6, p. 27. It will be seen that there is no halving- 

 wall in the latter as in the case of the stem-node. 



The genus Nitellopsis presents some variations from 

 the type of branchlet just described. There is usually 

 only one and never more than two nodes, and instead 

 of a whorl of comparatively small entirely lateral 

 bract-cells as in the genera already referred to, one or 

 two (rarely more) long, but still 1-celled members are 

 produced, at each node, on the inner side of the 

 branchlets. The apical cell, instead of being short 

 and conical, is elongated and cylindrical. 



The genus Tolypella presents further modifications. 

 In some species the sterile branchlets belong to an 

 extremely simple type, resembling the terminal process 

 of the pro -embryo, and consisting of a row of cylindrical 

 or allantoid cells joined end to end without any inter- 

 vening nodes, the apical cell in some species differing 

 little in shape or length from those below it, while in 

 others it is short and conical. The fertile branchlets 

 and, in some species, the sterile also, consist of one to 

 two cylindrical or allantoid cells, each succeeded by a 

 node, and surmounted by a terminal member formed of 



