.S48 Twenty-first report. 



Potamogeton filiformis Pers. should become P. marimifi L. Among many 

 modern botanists there has sprung np a very disconcerting practice, and a 

 needless one as well, of replacing old and well known names by those of a 

 later date, because, forsooth, the authors are not able to interpret to their own 

 satisfaction the older descriptions; hence the name is set aside as a "con- 

 fusing" name. There would be much less "confusion" if old names were not 

 discarded unless it could be proved beyond a shadow of doubt to what species 

 they do belong; this can not be done. To retain the old name, therefore, for 

 the species for which it had stood unchallenged for perhaps a century and a 

 half, more or less, would be not only the better plan but ranch less "confusing." 



PotatnogctMh ititerruptuH Kit. should be dropped as it has been shown by 

 Mr. St. John that this species if distinct from P. prctinatux L., does not occur 

 in this country. 



P. lonchites Tuckerman becomes P. Americmms C. & S. 



P. NuttalUi Cham, and Sch. becomes P. epihydrns Raf. 



P. spathulaeformis (Robbins) Morong. becomes /'. upathneformis 

 Tuckerman. 



P. Spirillus Tuckerman becomes P. dimorphtis Raf. 



P. Zizii Roth becomes P. angustifoUus Berch. & Presl. 



P. sosteraefoHus Schum. becomes P. compr€s»iis L. 



/'. Fricftii Ruprecht becomes P. mucronatufi Schrad. 



Other species and varieties credited to Michigan arc tlic fdllnwing: 



P. cpihyOrun var. Cayuiten^i* (Wieg.) Bonn. 



1'. Amenenntm var. Nfivafboran-iiHiH (Morong.) Kenn. 



7'. hvpleuroidfs Fernald. 



/'. HtrictlfoUuH Benn. 



P. riitiliiH Wi»lfg. In various slips at Detroit .lime L'!t, UHMt, No. l.O.'iOa. 



NAJADACEAE. 



Najas fiexilis (Willd.) Rost. & Schm. var. congesta n. var. Stems short, 

 much branched, and forming a dense, more or less globular mass, like a small 

 pin cushion, 1-3 inches in diameter. Detroit, R. ; Sept. 23, 1892, No. 1,312b. 



".Naias" .should be spelled with a "j", not with an "i". 



JUNCAGINACEAE. 

 Scheuchzoriaceae should become Juncaginaceae. 



ALISMOIDACEAE. 



Alismaceae should become Alismoidaceae. 



Kagittai-ia mgittaefolia L. becomes .S'. latifoUa Willd.; the forma angmti- 

 folia becomes 8. lutifolia f. gradHn (Pursh.) Robinson; the other forms 

 onmneratcd remain but the authority for them under 8. lafifoUa is Robinson 



