76 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 



Cakile edentula (Bigel.) Hook. Common on the sea strands 

 and along the brackish beach of Wallace Lake. J. Macoun; H. T. 

 Gussow (E); H. St. John, no. 1,241 (H). 



FL, Fr. August. 



RAPHANUS SATIVUS L. Established at the Main Life Saving Sta- 

 tion. H. St. John, no. 1,242 (H). 

 FL August. 



BRASSICA ARVENSIS (L.) Ktze. A weed near the Life Saving Sta- 

 tions. J. Macoun; H. St. John, no. 1,243 (H). 

 FL August. 



SISYMBRIUM OFFICINALE (L.) Scop. A weed near Life Saving 

 Station, No. 3. H. St. John, no. 1,244 (H). 

 FL, />. September. 



DROSERACEAE. 



Drosera rotundifolia L. Common in the wet dune hollows and 

 on the margins of the fresh-water ponds. J. Macoun; H. T. Gussow; 

 H. St. John, no. 1,245 (H). 



FL, Fr. August. 



D. longifolia L. In wet sand and bogs, found only by J. Macoun 

 (C. no. 21,187). 

 FL August. 



CRASSULACEAE. 



Tillaea aquatica L. Forming pure mats at the wet borders of 

 the fresh-water ponds. J. Macoun (C. no. 21,156); H. St. John, 

 nos. 1,246 and 1,247 (H). 



FL, Fr. July and August. 



The three collections of this plant from Sable Island show, in the 

 same clump, plants which have "nearly sessile" flowers and fruit, 

 and other plants bearing nearly sessile flowers in the upper axils and 

 peduncled ones in the lower axils. According to our present Ameri- 

 can treatments, we should have to recognize in these apparently 

 pure clumps two species. An examination of the American material 

 of Tillaea Vaillantii Willd. shows that in every known locality T. 

 aquatica occurs and occurs more abundantly, that its characters are 

 a matter of degree, not strictly definable. Consequently the author 

 feels that T. Vaillantii of American authors should be treated as 

 identical with T. aquatica. The inference must not be drawn that 



