1922] 



PFEIFFER MONOGRAPH OF THE ISOETACEAE 91 



distinct, and the air-channels (only two in the first leaves) are 

 produced. 



After development of sterile leaves for a few seasons, the 

 sporophyte begins to produce sporangia, as previously noted. 



Apogamy has been reported by only one worker, Goebel ('97), 

 who found examples in /. lacustris L. and /. echinospora Dur. 

 where the tiny leaf-producing shoots eventually giving rise to 

 roots replaced sporangia in position. These plantlets became 

 independent by the decay of the old leaf tissue. 



BIBLIOGRAPHY FOR MORPHOLOGY 



Belajeff, W. ('85). Die Antheridien und Spermatozoiden der heterosporen 



Lycopodiaceen. Bot. Zeit. 43:793. 1885. 



Bower, F. O. ('08). The origin of a land flora. London, 1908. 

 Braun, A. ('64). Ueber die Isoetes-Arten der Insel Sardinien, nebst allgemeinen 



Bemerkungen iiber die Gattung Isoetes. K. Akad. Wiss. Berlin, Monatsber. 



1863: 554-624. 1864. 

 Bruchmann, H. ('74). Wurzeln von Isoetes und Lycopodium. Jenaische 



Zeitschr. f. Naturwiss. 8:522. 1874. 

 Campbell, D. H. ('91). Contributions to the life history of Isoetes. Ann. Bot. 



5:231-256. pi. 15-17, 1891. 



Cesati & DeNotaris. ('58). Iiid. Sem. Hort. Reg. Bot. Gen. 1858. 

 Farmer, J. B. ('89). On Isoetes lacustris. Roy. Soc. London. Proc. 45 B:306. 



1889. 



, ('90). Morphology of Isoetes lacustris. Ann. Bot. 5:37-62. pi. 5-6. 



1890. 

 Goebel, K. ('97). Ueber Sprossbildung auf Isoetes blattern. Bot. Zeit. 37:1-6. 



/. 1-4. 1897. 

 Hegelmaier, F. ('72). Zur Morphologie der Gattung Lycopodium. Bot. Zeit. 



30:773-779. 1872. 



Hofmeister, ('62). The higher cryptogamia. Ray Soc. 1862. 

 Russow, E. ('72). Vergleichende Untersuchungen betreffend der Histologie der 



vegetativen und Sporen-bildenen Organe. Acad. Sci. St. Petersbourg, Mem. 



VII. 19:1. 1872. 

 Scott, A. H., and Hill, G. T. ('00). Structure of Isoetes hystrix. Ann. Bot. 14: 



413-454. 1900. 

 Smith, R. Wilson ('00). The structure and development of the sporophylls and 



sporangia of Isoetes. Bot. Gaz. 29: 225-258, 324-340. pi. 13-20. 1900. 

 Stokey, A. G. ('09). Anatomy of Isoetes. Bot. Gaz. 47: 311-335. pi. 19-21. 1909. 

 West, C., and Takeda, H. ('15). On Isoetes japonica A. Br. Linn. Soc. 



London, Trans. Bot. II. 8:333-376. pi. 33-40. f. 1-20. 1915. 



ECOLOGICAL RELATIONS OF THE GENUS ISOETES 



The genus Isoetes presents interesting ecological and geo- 

 graphical relations. The species prove very diverse in habitat, 

 ranging from lacustrine forms submerged in five or more feet of 

 water, to those strikingly xerophytic, exposed on dry hillsides. 

 Structural characters appear unusually constant, save in minor 

 points. Plants are perennial, and in some cases seem able to 

 withstand desiccation over long intervals, appearing after one or 



