NO. 9 MAXONIA, A NEW GENUS OF FERNS — CHRISTENSEN 3 



appressed firmly to the parenchyma, while the edges themselves are 

 bent upward. The two basal lobes now grow inward also and soon 

 reach each other or, even, one may widely overlap the other. The 

 now full-grown indusium is circular, apparently peltate, glabrous 

 or with a few glands along the edges, and very persistent. 



The characters mentioned — dimorphism, peculiar rhizomes, and 

 the unique development and morphology of the indusium — are to me 

 more than sufficient upon which to erect a new genus, which must 

 ., stand between Polybotrya and certain species of Dryopteris grouped 

 with D. amplissima. Granting that isomorphism is a more primitive 

 character than dimorphism, the new genus represents a more recent 

 type than Dryopteris, although it has not progressed so far as Polybo- 

 trya, with which genus it has most characters in common. It still 

 shows such dryopteroid characters as having indusia and sporangia 

 confined to the back of the veins. In its evolution from Dryopteris 

 toward a more specialized type it has not progressed so far that all 

 characters have become fixed. Thus the dimorphism generally 

 ascribed to the species is, as mentioned, not a stable character. The 

 occasional subdimorphous leaves point definitely to dryopteroid 

 ancestors with isomorphous leaves. 



It is a special pleasure to me to have got permission to dedicate 

 this interesting new genus to Mr. William R. Maxon, Associate 

 Curator of the U. S. National Herbarium, who has contributed very 

 much to our knowledge of the ferns of tropical America by his ex- 

 cellent collections of these plants in Jamaica, Cuba, and Central 

 America, and by numerous papers in which he has succeeded in 

 unraveling with acumen several intricate groups of that difficult 

 division of plants. 



MAXONIA C. Chr., gen. nov. 

 Type : Dicksonia apiifolia Swartz, the only species known. 



MAXONIA APIIFOLIA (Swartz) C. Chr., comb. nov. 



Dicksonia apiifolia Swartz, Journ. Bot. Schrad. 1800'': 91. 1801. 

 Dryopteris apiifolia Kuntze, Rev. Gen. PI. 2: 811. 1891 ; Maxon, 



Contr. U. S. Nat. Herb. 13: 39. 1909. 

 Aspidium ascendens Hew. Mag. Nat. Hist. II. 2: 463. 1838; Hook. 



Sp. Fil. 4: 32. pi. 224. 1862. 

 Polystichuni apiifolium C. Chr. Ind. Fil. 578. 1906. 



