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XXI. Obfirvatlons on the Genus of Porella, and the Phafcum caulefcens 

 of Linnaus. By Mr, James Dickfon, F. L. S. 



V Read May 5, 1.795. 



THE genus of Porella, fiift eflabllihed by Dlllenius, and from 

 him copied by Linnaeus, who never faw the plant, had long 

 appeared to me to be very doubtful : 1 had, however, an oppor- 

 tunity, fome time ago, of fatisfying myfclf on this fubjedt. I 

 happened to receive fome mofTes as package to plants from Ame- 

 rica; and, upon examining them, found a Jungermannia and a 

 Splachnum in fru£lification. I fufpedted the Jungermamia to be the 

 fame with the Porella of Dillenius ; but this could not be afcertained 

 without a£lually comparing the two fpecimens, which I had an 

 opportunity of doing by the indulgence of Dr. Sibthorp, of Oxford, 

 who permitted me to compare my mofTes with Dillenius's original 

 coUedlion ; and, upon the moft careful examination, I found my 

 Jungermannia to agree exa6lly with his Porella, but could find no 

 fructification .upon his fpecimen. 



As I have no doubt that my Jungermannia and his Porella are one 

 and the fame plant, I fhall next endeavour to trace how Dillenius 

 has fallen into this error ; for the plant has exadlly the habit of 

 a Jungermannia. — This was, probably, by receiving an imperfect 

 fpecimen ; as the vagina, when damaged either by the weather or 

 by infefts, after the tender flower had fallen off, would very much 

 refemble the capfule which he has figured. 



His figure of the plant is too much crowded with leaves ; but in 

 his original drawings in the pofleflion of Sir Jofeph Banks, the 



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