[Vol. 9, 1922] 

 226 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



EXPLANATION OF PLATE 



PLATE 16 



Fig. 19. Isoetes melanospora Engelm. Megaspores. 



Fig. 20. I. lithopliila Pfeiffer. Megaspores. 



Fig. 21. I. flaccida Shuttlew. Megaspores. 



Fig. 22. I. flaccida var. alata (Small) Pfeiffer. Megaspores. 



