Arber.—On the ‘ Squamulae Intravaginales ’ of the Helobieae. 35 
Fig. 3. Potamogeton natans, L. Figs. 3 a-e, series of transverse sections from below upwards 
through apical bud including two successive leaves and the squamules within them ( x 47) ; lettering 
as in Fig. 1, see also explanation in text. Figs. 3 F and G show further stages in the development of 
the second leaf and the squamules. Fig. 3 F, from a broken section, somewhat reconstructed as regards 
lig. s.i and sq. a on right. . 
POTAMOGETON 
D 3 
