188 EDWAKD C. JEFFREY ON 



same family, and even in different species of the same genus. The writer consequently 

 is of the opinion, that the Sphenophyllales cannot any longer, on that ground, be 

 regarded as a separate phylum, but must be included with the Equisetales as an addi- 

 tional order, thus: — 



Sphenophyllaceae. 

 Equisetales Calamitaceae. 

 Equisetaceae. 

 . 5. The branches of the Calamites did not, as has been stated in recent years, arise 

 above the nodes, but, like those of tlie Equisetaceae, originated either more or less 

 exactly from the center of the ring of nodal wood, or from its lower border. 



G. The more conspicuous series of nodules on the medullary casts of the Calamites 

 are not impressions of Williamson's infranodal canals, but on the contrary of the short 

 cylindrical medullary cavities of modified rhizophorous branches, homologous with those 

 of living Equiseta. 



7. Nodal periderm is present in certain species of Equisetum and is comparable 

 to that described by Williamson and Scott as occurring in the nodal diaphragms of 

 Calamites. 



This investigation was completed in the Cryptogamic laboratory of Harvard 

 university, and the writer offers his best thanks to Dr. W. G. Farlow and Dr. Roland 

 Thaxter for their courtesy and advice. He is also under obligations to' Dr. G. L. 

 Goodale for material and the use of photographic apparatus belonging to his department, 

 and to Dr. B. L. Eobinson for cones of a large number of species of Equisetum from the 

 collections in the Gray herbarium. 



