FOREIGN DRIFT OF THE TURKS ISLANDS 161 



is unable to displace the air within, and the " stone " thus becomes 

 buoyant. 



Ipomgea tuberosa, L. 



Much interest is attached to these West Indian drift seeds or 

 fruits, since they remained for nearly three centuries without a 

 botanical name, though often mentioned by the earlier botanists 

 and other contemporary writers as figuring amongst the foreign 

 drift stranded on the Orkney Islands and the Hebrides. Clusius 

 (1605), C. Bauhin (1623), Sloane (1695), Petiver (1702), the two 

 Wallaces in their descriptions of the Orkneys (1693-1700), and 

 Pennant in the account of his tour in the Hebrides (1772), all refer 

 to them, but not one of them was acquainted with their source,, 

 although some, like Sloane, make correct surmises. They were 

 content to describe and sometimes rudely figure them. Petiver's 

 use of the name " Faba Orcadensis," though very appropriate in a 

 popular sense, since the earliest recorded drift specimens came from 

 that group, served rather to increase the mystery, which was not 

 solved until Hemsley identified them with Ipomcea tuberosa, L., in 

 his paper in the Annals of Botany for 1892 (Vol. VI.). Superstition 

 played its part in the story of these strange-looking gifts from the 

 sea; and, as we have seen in Chapter II., the women of the Hebrides 

 are stated to have sought relief during the pains of childbirth by- 

 clenching one of them in the hand. 



These fruits or seeds (their particular designation being uncertain) 

 are about an inch across, depressed-globose in shape, yet slightly 

 squarish in outline. The ebony-black hue, the hard, bony, polished 

 shell, the four-lobed, or rather four-grooved, upper surface, and the 

 large scar underneath, are characters that distinguish them from all 

 other drift seeds and fruits. Grisebach states that Ipomosa tuberosa 

 is distributed over the West Indian islands and occurs on the tropical 

 American mainland (Mexico to Guiana), as well as in tropical Africa 

 and the East Indies. Hemsley in the paper above named remarks 

 that although it is usually regarded as a native of tropical Asia, 

 Africa, and America, its Old World form was separated by Mr. C. B. 

 Clarke under the name of kentrocaulos. " It is not " (he writes) 

 " essentially a shore plant, but rather a climber of lofty trees." Nor- 

 mally there are four separable seeds as in typical Ipomoeas, but 

 they are closely compressed and form a spheroid. Not infrequently, 

 according to Hemsley, only one seed is developed, which " assumes 

 the size and nearly the shape of the four seeds combined," and 

 adapts itself to the size and shape of the seed-vessel, the original 

 complement of four seeds being indicated by four furrows. It may 

 happen, as in the case of one of the typical drift specimens examined 

 by me, that there is an appearance of two cells, each containing an 

 embryo. Here we seem to be concerned with a fruit rather than 

 with a seed. There is evidently much to be learned about the con- 

 ditions under which this abnormal development takes place. It 

 may be added that Grisebach makes no allusion to it in the descrip- 

 tion he gives of the species, and that seeds gathered by me from living 

 plants in Jamaica displayed no such peculiarity. 



M 



