STRUCTURE AND DEVELOPMENT. 37 



each bract-cell (styled diplostichous), while in a few 

 extra-European species there are three to each bract- 

 cell (styled triplostichous). In all the European 

 species except G. tomentosa the lowest limb of the 

 branchlet is covered entirely by a cortex originating 

 from the lowest free node and therefore growing 

 downwards. In G. tomentosa there is an entire or 

 partial circle of cortex-cells growing upwards from 

 the node at the base of the branchlet. In a small 

 number of extra-European species, the sub-section 

 Gy mnojpodea of the Triplostichse, the lowest limb of 

 the branchlet is ecorticate. 



The cortical-cells and the bract-cells arise from a 

 series of secondary nodes, developed from the peri- 

 pheral cells of the branchlet-node, which divide as 

 shown in Fig. 6 v, a small portion of each remaining 

 as a rest-cell, i. 



There is usually a correspondence in the shape and 

 extent of development of the spine-cells, stipulodes 

 and bract-cells, all these appendages being usually long 

 or short, acute or obtuse, bulbous-based or otherwise, 

 in the same form and often also in the same species. 

 There are, however, exceptions to this, as e.g. G. 

 vidgaris var. longibracteata, in which the anterior 

 bract-cells are very long, while the stipulodes and 

 spine-cells are but little developed. Not infrequently 

 an abnormal example of each of these appendages 

 occurs in the shape of a two-lobed cell. 



As already stated reserves of starch 

 are accumulated in enlargements pro- 

 ceeding from the lower stem-nodes and root-nodes, 

 which are styled bulbils. They are usually produced 

 when the plant is growing in fine slimy mud, are 

 whitish in colour, and form the basis of two forms of 



