138 MR. J. COSMO MELVILL ON THE 



(3) "A non-ancestor is always a non-ancestor of all an- 

 cestors, and an ancestor of none but non-ancestors." 



(4) " A non-descendant is a descendant of none but non- 

 descendants, and a non-descendant of all descendants." 



(5) "Among non-ancestors are contained all descendants 

 of non-ancestors, and all non-ancestors of descendants." 



(6) "Among non-descendants arecontained all ancestors 

 of non-descendants, and all non-descendants of ancestors." 



XIII. List of the Phanerogams of Key West, South Florida, 

 mostly observed there in March, 1872. By J. Cosmo 

 Melvill, M.A., F.L.S. 



Eead before the Microscopical and Natural-History Section, 

 February 13, 1882. 



The flora of this small island is limited and, naturally, to 

 a great extent, maritime. In the year 1875 I recorded, 

 in the ' Journal of Botany/ a catalogue of the Algse — it is 

 by no means so rich, proportionately, in flowering plants 

 or ferns. 



Key West, which is entirely of coral formation, consti- 

 tutes one of many small reefs or " keys " which extend 

 from Biscayne Bay westward to the Tortugas. Of these 

 islets, this, which measures some seven miles in length by 

 one to one and a half in breadth, is the only one inhabited, 

 and it is not likely that the others would present many 

 botanical novelties, though but few of them have been 

 explored. Boca Chica, the next island, is separated at low 

 water by only a very narrow channel. It is densely 



