195 



of this complicated generic tangle of affinities, we are unable to 

 follow the Continental botanists in this matter. Absolute con- 

 sistency is not to be looked for in generic separation, but when 

 Diplaziiwi and Athyrium are kept distinct from Asplenuan by 

 such meager and graduated characters, Elaplioglossum from 

 Acrostic/mm, and Polysticlmm from Dryopteris, we see no consist- 

 ency in uniting Menisciiim with Dryopteris, or Campyloneiiruni 

 with Polypodmm. There is perhaps more reason for the union of 

 P]iegopteris * and Dryopteris, since the difference is one which 

 concerns mainly indusial characters. In any case, a knowledge 

 of the European and United States species merely is insufficient 

 to form a reasonable basis for a proper settlement of the question, 

 and words based on such a knowledge are mere waste of breath. 

 Among the necessary changes we note the following : 



Ceratopteris pteridoides (Hook.) 



Parkeria pteridoides Hook. Exot. Fl. 2: pi. 147. 1825. 



After much study of living and herbarium material we are con- 

 vinced that the determinable American material we have seen 

 extending in range from Guiana, the type locality of Hooker's 

 species, to Florida represents a plant entirely distinct from the 

 species of the Old World which was included by Linnaeus under 

 his two species, AcrosticJmui siliqiiosinn and Acrostic/mm tlialic- 

 troides, and commonly known under the name Ceratopteris tJialic- 

 troides since Brongniart established that genus. Hooker's type 

 and excellent figures well represent the plant occasional in our 

 American tropics and often seen in cultivation. 



The American plant has leaves much less divided than its Old 

 World congener and is everywhere excessively proliferous, grow- 

 ing young plantlets over its surface at the sinuses of the leaves, 

 and even in the axils of the sporophyls. Christensen follows the 

 customary reference of the American plant to Ceratopteris tJialic- 

 troides (L.) Brongn., but if, as appears, there is only a single spe- 

 cies in the Old World, that name is not a valid one. There is a 

 slight suspicion that the Old World species may also appear in 



* In the new catalogue of British plants (1907) the species of Phegopteris are still 

 retained in the genus Polypodiuni in accordance with the ancient Linnaean conception 

 of that genus. 



