[Vol. 2 

 34 ANNALS OP THE MISSOURI BOTANICAL GARDEN 



by us on Desecheo, together with one made by Professor F. 

 L. Stevens and Mr. W. E. Hess in May, 1913, shows that 

 the spermatophytes of Desecheo number about 90 species; 

 further intensive exploration might reveal a few more. A 

 single species of fern was seen, four species of mosses, and 

 two species of hepatics. As there is no probability of this 

 little island ever having been a part of the Porto Rico main- 

 land, its plants must have reached it by natural agencies ; there 

 are probably as many fungi and lichens as of other land 

 plants collectively, so the total land flora of Desecheo probably 

 includes at least 200 species. 



Mona Island, lying about thirty miles to the southwest of 

 Desecheo, in the middle of the Mona Passage between Santo 

 Domingo and Porto Rico, has an area of approximately twenty 

 square miles. Prior to our visit, only one botanical collection 

 had been made there, when it was visited by Professor F. 

 L. Stevens in 1913, at which time he obtained specimens of 

 about 150 species of flowering plants, and gave especial atten- 

 tion to the parasitic fungi. The considerable land area of 

 this island made a complete knowledge of its flora desirable, 

 from the standpoint of geographical distribution of West 

 Indian plants, and we were able to devote five days to collect- 

 ing. The greater portion of Mona is a limestone plateau 

 elevated from 125 to 175 feet, the surface of this plateau being 

 nearly level and devoid of hills; its soil is very sparse, con- 

 sisting altogether of reddish loam in depressions of the lime- 

 stone surface, and not of considerable extent at any point 

 visited by us. The limestone is evidently very porous, and 

 there are no streams or ponds, and only a single spring was 

 seen; the limestone is honeycombed with caves and caverns, 

 some of them of considerable size. The rainfall is evidently 

 considerable, but there are no records of its amount. Despite 

 the paucity of soil, the whole plateau is rather densely 

 covered with shrubs and low trees of a considerable number 

 of species, their roots, for the most part, penetrating into 

 crevices of the limestone. Herbaceous vegetation is restricted 

 to comparatively few species. Eight species of cacti inhabit 

 this plateau, and in places are very abundant, the snowy cactus 



