[Vol. 9, 1922] 

 228 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



EXPLANATION OF PLATE 



PLATE 17 



Fig. 23. Isoetes Howellii Engclm. Megaspores. 



Fig. 24. I. Bolanderi Engelm. Megaspores. 



Fig. 25. I. Tuerclclieimii Brause. Megaspores. 



Fig. 26. I. mexicana Underw. Megaspores. 



Fig. 27. I. melanopoda Gay & Dur. Megaspores. 



Fig. 28. I Butleri Engelm. Megaspores. 



