MISCELLANEOUS PLANTS 



173 



from which they could readily be swept off by the waves and carried 

 away in the currents. However, my experiments in the Turks 

 Islands indicate that they possess limited floating powers. Picked 

 up by the waves, and washed off the beach, they would sink in 

 from two to four days. Prolonged drying for a year and more 

 adds but little to their buoyancy, half of them sinking in two days, 

 whilst the few remaining afloat after a week are only floated up by 

 adherent air-bubbles. The achene removed from the involucre has 

 initial buoyancy, but sinks within four days. Though unsuited for 

 direct distribution by the currents over broad tracts of sea, these 

 small fruits might be carried great distances in the crevices of a 

 drifting log. They would readily be washed with the sand into the 

 crevices of timber temporarily stranded on a coast. 



The achene shut up in the dry involucre would not be likely to 

 tempt sea-birds, and the fruits do not attach themselves to plumage. 

 The achene is 2-5 to 3 mm. in length. The length of the fruit with 

 the persistent involucre is 4 mm. 



The genus holds fifteen known species, of which all but one are 

 confined to the New World. The exception is a widely spread 

 Mediterranean shore plant (Ambrosia maritima, L.) which extends 

 to the coast of Senegal. Certain of the species range far and wide as 

 waste plants and weeds in the American continent and in the West 

 Indies. Some North American species frequent estuarine marshes, 

 whilst others prefer the sand-prairies of the interior and the borders 

 of salt swamps in inland regions (Harshberger). 



I found Ambrosia crithmifolia thriving on six of the ten cays of the 

 Turks Islands, and reference to it in this connection will be found in 

 the chapter on the flora of these islands. Mr. Lansing's observations 

 on the Florida sand-keys, where he found it growing on five of the 

 nineteen keys examined, indicate that it is one of the earlier plants 

 to occupy land newly gained by accretion from the waves. Yet the 

 fact that it has not been observed in Bermuda, which has received so 

 many West Indian strand plants, militates against the efficacy of the 

 currents in transporting it across broad tracts of ocean. 



Anacardium occidentale, L. (Cashew-nut) 



The nuts of this West Indian tree, which is only indigenous in the 

 New World, do not form a feature in the beach-drift of these regions. 

 On one occasion I found a solitary decaying nut on a Jamaican 

 beach; but that alone could not entitle it to be regarded as a drift 

 fruit. Yet it is interesting to note that Gunnerus, who lived in the 

 middle of the eighteenth century, found this fruit on the Norwegian 

 coast; but Sernander in his book on the Dispersal-Biology of the 

 Scandinavian flora (p. 117) tells us that it has not been found since. 

 Hemsley, who quotes Linnaeus on this point, says that the seed was 

 in a living condition, and he places the fruit among those certainly 

 or probably distributed by currents (Chall. Bot., I., 43 ; IV., 278, 305). 



This Norwegian drift fruit has puzzled me much, since Linnaeus 

 gives no other particulars concerning it. The large fleshy peduncle 

 could not possibly be here concerned, unless it was thrown over 



