280 



BOTANY 



B 



The gametophyte is much like that of the Polypodiaceae, but very 

 often develops upon its upper surface characteristic bristles. 



The Cyatheacese are the most 

 imposing of all existing Pteri- 

 dophytes, and their Palm-like 

 trunks and crowns of gigantic 

 leaves are conspicuous features 

 of the tropical mountain-flora. 

 About two hundred and fifty 

 species have been described, some 

 of which are extra-tropical, espe- 

 cially in the southern hemi- 

 sphere. The most important 

 genera are Cyathea, Alsophila, 

 Dicksonia, and Hemitelia. 



Family 7. Parkeriaceae 



Poly podium falcatum. 



The single representative of 

 this family, usually included 



Pinna with sori, sp ; natural size. B, with the Polypodiaceae, is a pe- 

 Pteridium aquilinum. C, Asplenium culiar aquatic Fern Ceratopteris 

 fihx-faimina (X 3). 7 .* 



tlmhctroia.es, widely distributed 



in the Tropics, and reaching our limits in Florida. The annulus is 

 sometimes completely suppressed. 



Family 8. Polypodiacese 



The Polypodiaceae include a very large majority of all existing 

 Pteridophytes, and are the most modern representatives of the sub- 



FIG. 248. A, Aspidium spinulosum (X 2). B, Struthiopteris Germanica, cross- 

 section of young fertile pinna (X 25) ; s, sorus. 



kingdom. The greater number of Ferns of cooler regions are Poly- 

 podiaceae, and occasionally, as in the case of Pteridium aquilinum, 



