PLANTS OF THE TRES MARIAS ISLANDS. 



By J. N. ROSE, 

 Assistant Curator, Division of Plants, U. S. National Museum. 1 



The Tres Marias, lying about 65 miles off the west coast of Mexico 

 in about 22 north latitude, are among the last of the west coast islands 

 to be studied. All the others have yielded valuable botanical results, 

 but almost nothing has been known of the flora of these islands 

 except in a commercial way. Several botanical expeditions had been 

 planned to explore the islands, but heretofore none had succeeded in 

 reaching them. They are out of the line of traffic, although some of 

 the smaller steamers stop now and then for fuel, and small boats 

 occasionally ply between the islands and San Bias. They are usually 

 visited during the dry season, as it is dangerous to attempt the passage 

 during summer and autumn. 



Mr. Xelson visited the islands at the very close of the dry season, 

 when the vegetation is at its poorest, and this accounts for the small 

 number of species collected. His collection contains 154 numbers (Nos. 

 4179 to 4333) and 136 species, mostly from Maria Madre, the largest 

 of the islands, and only a few from Maria Magdalena and Maria 

 Cleof'a. In the subjoined list the plants are from Maria Madre unless 

 otherwise stated. 



There are no cultivated plants on the islands, except one or two 

 grasses. Fithecolobium dulce, perhaps introduced, is common and 

 much prized for its delicious fruit. The exportation of Spanish cedar 

 (Cedrela sp.) has long been the chief source of income for the islands, 

 but the available supply of this timber is now nearly exhausted. The 

 flora is purely tropical and does not differ essentially from that of the 

 adjacent mainland. Many of the species have not been reported from 

 the mainland opposite, but this is doubtless because the flora is not 

 well known, since these species have been collected either farther north 

 or south. One hundred and twelve species are named below, of which 

 11 are new. Many of them have a wide distribution in tropical 

 America; all but 6, except the new species, have heretofore been 

 reported from Mexico; 24 range northward into the United States; 

 64 extend into Central America; 61 into South America; 44 into the 

 West Indies^ and 21 are found in the Old World. 



Published by permission of the Secretary of the Smithsonian Institution. 



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