1900] SPOROPHYLLS AND SPORANGIA OF ISOETES 341 
22. The sterile leaves in a majority of cases have aborted 
sporangia. When these have made any considerable develop- 
ment they are usually found to show the characters of megaspo- 
rangia. 
23. The sporangia after all cell divisions have ceased continue 
to increase in volume, apparently by the osmotic properties of 
the substances surrounding the young spores. 
24. An attempt to relate the change from megasporophylls 
to microsporophylls to an exhaustion of the nutritive cortical 
cells formed in the preceding year was unsuccessful. 
25. To secure a more consistent nomenclature it is proposed 
to employ the term archesporium in speaking of a pteridophyte 
sporangium to designate the superficial cell or cells from which 
the sporogenous tissue takes its origin. 
I am indebted to Professor John M. Coulter, of the University 
of Chicago, at whose suggestion the investigation was under- 
taken, for helpful suggestions and criticisms. Acknowledg- 
ments are also due to Dr. C. J. Chamberlain. 
McMaster UNIVERSITY, 
Toronto, Canada 
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