Fig. 38: Potamogeton Berchtoldii: a, habit, showing dense, short, somewhat spread- 

 ing leaves, X %; b, young flowering spike surrounded by sheathing stipules, X 5; c, 

 sepaloid connective, X 12; d, habit of a plant with leaves longer and more linear- 

 setaceous than those of plant in a, X %; e and f, typical leaf tips, showing venation, 

 X 8; g, achene (longitudinal section), x 12; h, achene, showing the rounded obscurely 

 keeled back and the marginal erect beak, X 12; i, winter bud, X 2. (From Mason, 

 Fig. 25). 



