POLYPODIACEAE 21 



It occurs in nearly all the high-pineland hammocks, but in 

 those where arboreous vegetation is so dense as to cause 

 twilight in mid-day and whose floor is honeycombed with 

 lime-sinks the development of this delicate fern is sur- 

 prising. There are exceptions to this rule of grow- 

 ing so luxuriantly only in dense shade, for in occasional 

 localities where storms have carried away the tops of 

 trees thus exposing areas of several square rods in ex- 

 tent, this beautiful fern takes almost complete posses- 

 sion of the ground, forming a carpet over the hammock 

 floor. The plant grows only sparingly in Eoyal Palm 

 Hammock and apparently never develops as luxuriantly 

 as it does in the hammocks of the neighboring pinelands. 

 Another species Adiantum melanoleucum grows in a 

 hammock on Long Key. 



Curiously enough, this, although one of the more 

 common tropical ferns in Florida, was not discovered 

 there until 1877. It ranges northward to the upper 

 part of the peninsula, and is widely distributed in 

 insular and continental tropical America. 



8. BLECHNTJM L. 



Coarse terrestrial or rarely epiphytic often swamp- 

 plants. Leaves single or clustered on the horizontal or 

 erect rootstock: blades rather narrow in proportion to 

 their length, pinnatifid or pinnate, the segments or 

 leaflets entire or toothed, those without spores with free 

 veins, the spore-bearing ones with the veins connected 

 near their bases by a transverse receptacle which bears 

 a narrow sorus parallel to the midrib and usually near 

 it. Indusia membranous, linear, distinct from the edge 

 of the leaf -blades and at length reflexed from the inner 

 side. About twenty species, native of the south-tem- 

 perate regions and the tropics. 



