STEUCTURE AND DEVELOPMENT. 29 



a string of elongated celJs, the apical cell being in some 

 species short and conical. At each node of the branch- 

 let several lateral members are produced, differing 

 from the bract-cells of the Charese in that they consist 

 of a longitudinal series of cells. 



The genus Nitella presents a different feature. The 

 antheridium is terminal and at each branchlet-node 

 where one is present the axis becomes interrupted and 

 two or more (rarely only one) lateral members arise. 

 The branchlet in the various groups of this genus 

 presents a great range in degree of complexity. The 

 simplest form consists of a long internodal cell, 

 followed by a single node which gives rise to 1-4 

 lateral 1 -celled members, and where no antheridium 

 is present to a 1-celled terminal segment. This 

 terminal segment resembles the lateral members and 

 it is only upon close examination that it is seen that 

 the branchlet is not genuinely forked. In more com- 

 plex types there are a number of nodes from which 

 secondary axes are produced, which in their turn also 

 give rise to lateral members, so that tertiary and even 

 quaternary axes may occur. The terminal member 

 may consist of a single cell, or of two to six cells. In 

 no British species does the number exceed three. In 

 a very few species in addition to the normal branchlets 

 smaller accessory branchlets are produced at the same 

 stem-nodes, above and below the normal branchlets. 

 The only British species presenting this type is N. 

 hyalina. 



At the base of and below the branch- 

 lets in the Ohareas, with the exception 

 of Nitellopsis, there arises a single or double circle 

 of organs called stipulodes, varying considerably 

 in size, always much shorter than the branchlets, 



