144 PLANTS, SEEDS, AND CURRENTS 



Atoll, after a drifting voyage of at least 700 miles and a passage that 

 would require at least seven or eight weeks, renders this route across 

 the Atlantic possible for the seeds of Carapa guianensis. 



MAMMEA AMERICANA, L. 



This well-known West Indian tree belongs to a small genus which 

 has a remarkable discontinuous distribution. It holds six known 

 species, of which three are tropical American and three are peculiar 

 to Madagascar (Index Kewensis). In belonging to a genus of this 

 description Mammea americana resembles several other trees that 

 are referred to in this work in connection with drift. These dis- 

 continuous tropical genera have a great importance. 



According to Grisebach and Urban this tree, which is confined to 

 the New World, ranges from Cuba and Jamaica to Brazil, and is 

 widely distributed in the greater and smaller West Indian Islands. 

 It grows in the lower mountain forests of Jamaica, the locality where 

 I made its acquaintance, and it is as a West Indian forest tree that 

 it finds its natural station (see also Harshberger's work, p. 688, 

 concerning its station in the islands of St. Thomas and St. John). 



The large russet-coloured drupes, four to six inches across, con- 

 tain usually two or three large " stones," each consisting of a fibro- 

 ligneous endocarp encasing the seed. Inside the tough skin of the 

 fruit is a firm fleshy pulp. The fresh " stones " have no buoyancy; 

 but since the pericarp is buoyant, it is probable that the fruit would 

 float at first, though not for long, as the soft coverings would soon 

 decay. The " stones " evidently acquire their floating power when 

 drying on the ground after being freed from the fruit, the buoyancy 

 being due partly to the dried endocarp and partly to the unfilled 

 space arising from the shrinking of the seed. Though edible in a 

 general sense for man, the fruits are more appreciated by animals. 

 In Jamaica, according to Sloane, wild swine feed upon them. When 

 dried after removal from the fruit the " stones " have a rough, pitted 

 exterior; but as they occur in the beach-drift, after undergoing the 

 wear-and-tear of sea transport, their surface is usually smooth and 

 marked by interlacing fibres which give them a peculiar appearance. 

 In this condition the " stones " are generally two and a half to three 

 inches long and ovoid in shape. 



I found the " stones " in the beach-drift on the north coast of 

 Jamaica (as at St. Anne's), on the south-east coast of Tobago, on 

 the south coast of Trinidad, and on the Turks Islands. In the 

 group of islands last named they form a regular constituent of the 

 beach-drift, and came under my notice wherever the drift had 

 collected in any quantity, as on Grand Turk, Cotton Cay, Salt Cay, 

 and Greater Sand Cay ; but I rarely observed more than two or three 

 on each beach. In all the four West Indian localities above men- 

 tioned, the " stones " of the beach-drift gave little promise of being 

 effective agents in the dispersal of the species by currents. Usually 

 in half the cases the seed had decayed away; whilst in the rest, 

 though the seed appeared sound, its hard consistence and dead- 

 looking aspect on section did not indicate the retention of the germin- 



