184 PLANTS, SEEDS, AND CURRENTS 



this article, as shown by the report of Mr. F. H. Watkins on the salt 

 industry of the Turks Islands (Colonial Reports, Miscell., No. 56, 1908). 

 As the plant thrives around the creeks and ponds that supply the 

 salt-pans on Grand Turk, it is not improbable that the original 

 achenes might have been contained in salt shipped to Bermuda. 

 But against this view there is the fact that the plant was cultivated 

 before 1699 in England at Hampton Court from Bermudian sources 

 (Chall. Bot., II., 45). On the whole it would seem most likely that 

 the original fruits were transported to the Bermudas buoyed up 

 in the miscellaneous Gulf Stream drift that is stranded there in 

 quantities. 



Cakile 



My remarks on this genus will be mainly directed to the question 

 of dispersal. The history of the investigation of the genus is sym- 

 bolical of the history of its specific differentiation as a single wide- 

 ranging variable type. At first, when the known forms were few, 

 the genus was often regarded as monotypic, or as holding only one 

 species with fixed geographical varieties in the Old and New Worlds 

 and typified in Cakile maritima, the well-known European form. 

 In the next stage each side of the North Atlantic was credited with 

 a solitary species. As the inquiry proceeded, more particularly 

 after Asa Gray had separated the two common American plants 

 from the European C. maritima, the balance of distribution was 

 transferred to the American side of the Atlantic. In that direction 

 the later investigations have in the main advanced ; and whatever 

 view we take of the limits of the species it cannot be gainsaid that 

 the genus is preponderantly American. 



There is, however, a disconcerting lack of agreement amongst 

 later investigators as to the limits of the species. Most of the diffi- 

 culties seem to be due to the different results obtained from the use 

 of the leaf and fruit characters in the distinction of forms. Having 

 encountered such difficulties, Dr. Millspaugh made a discriminative 

 study of the fruits and seeds of the specimens in the principal herbaria 

 of the United States and defined the relations of the American 

 plants with those across the Atlantic, the results being published 

 under the title of Plantce Utowana? (Part I. a) by the Field Columbian 

 "Museum (Chicago, 1900). He distinguished ten species, eight being 

 American and two European, no species occurring as an indigenous 

 plant on both sides of the Atlantic. In the Index Kewensis, including 

 the supplements up to 1910, ten species are enumerated, of which 

 seven are exclusively American; but only six of the species given 

 by Millspaugh are named. The more recent investigators, including 

 :Schulz in Urban's Symbolce Antillance (1903), seem to have laboured 

 ^towards the reduction of the species, and I note that Fawcett and 

 Rendle in their Jamaican Flora (1914) speak only of four species 

 in the genus. 



However, these differences of opinion concerning the limits of 

 the species do not affect the distribution of the genus, which may be 

 regarded as restricted, with the exception of a representation in 

 the region of the Great Lakes of North America, to the western 



