WEATHERBY. — AMERICAN FORMS OF LYCOPODIUM COMPLANATUM. 413 



South American) are connected by various intermediates, but, in 

 their extreme development, are sufficiently diverse to warrant varie- 

 tal distinction. Indeed, since Humboldt and Bonpland described their 

 Lycopodium thyoides in 1810, it has been recognized by most botanists 

 that some, at least, of the tropical material differed from typical L. 

 complanatum of northern Europe and North America ; and L. thy- 

 oides has been rather generally maintained as a variety, differently 

 defined by different authors. Neither its relation to the northern 

 forms, however, nor its exact identity in regard to the other tropi- 

 cal form seems to have worked out with entire clearness. Lloyd and 

 Underwood, in their Review of the North American Species of Lyco- 

 podium, 2 called attention to the habital difference between Mexican 

 and Central American, and northern specimens ; but, partly owing, no 

 doubt, to their reluctance to describe varieties, carried their studies no 

 further. Dr. Christ, 3 in a brief but clear note, has pointed out the 

 distinctions between the two southern forms ; but he seems to be in 

 error in referring the prevailing South American form to typical L. com- 

 jylanatum. The plant of northern Europe and America which, as Prof. 

 Fernald has shown, should be regarded as the type of the Linnaean 

 species, is low, and habitally as well as in the characters of its branchlets 

 and their leaves, quite different from the taller South American plant. 

 Dr. Christ seems also to have been in error in identifying the other tropi- 

 cal extreme, which has broad branchlets and long leaves with con- 

 spicuously spreading tips, with L. thyoides H. & B. The original 

 description of this species in Willd. Sp. PL v. 18, emphasizes rather 

 strongly the appressed leaves. 4 In view of the facts that the type 

 specimens were from Venezuela, and that the appressed-leaved form is 

 apparently much the more common throughout South America, it 

 seems best to follow the first diagnosis, and to restrict L. thyoides 

 to that form. 



In spite of their complete geographic separation, there is nothing to 

 warrant the segregation of the tropical forms as separate species. The 

 characters which distinguish them are of too little importance in them- 

 selves and too inconstant. They are rather to be considered as ex- 

 treme developments of tendencies which are traceable also in occasional 

 specimens of the northern plant, but are there not so strongly developed. 

 The earliest varietal designation of the South American plant and that 

 which, under the Vienna Rules, it should bear, is L. complanatum, 

 ft tropicum Spring, based on L. thyoides H. & B. The other, prevail- 

 ingly Mexican, extreme seems to be without an available name. 



2 Bull. Torr. Bot. Club, xxvii. 165 (1900). 



3 Bull. Herb. Boiss., ser. 2, ii. 707 (1902). 4 " foliis semper adpressis." 



