THE GREEN AI.GAE OF NORTH AMERICA 415 



The appearance of the plant is perfectly described by the 

 specific name p/itmaris, which now, unfortunately, must be 

 given up ; only quite aberrant forms are liable to be mistaken 

 for anything else. The four forms described below occur 

 within our limits ; forma brcvipcs and forma longipes are found 

 everywhere with the type, of which they are merely extreme 

 forms ; forma longiseta is from Jamaica, forma Farlowii from 

 Florida. 



Forma BREVIPES (J. Ag.) Svedelius, 1906, p. 114, fig. 7 ; C. 

 pi it ///art's forma brevipcs Weber, 1898, p. 294. Frond simple, 

 the pinnules extending to the base of the rachis. 



Forma longipes (Ag.) nov. comb. ; C. plnmaris forma longipes 

 Weber, 1898, p. 295. Frond branching, pedicelled, without 

 pinnules for a long distance at the base. 



Forma LONGISETA (J. Ag.) Svedelius, 1906, p. 114, fig. 10 ; 

 C. plum aris forma longiseta Weber 1898, p. 295. Pinnules fine, 

 long (2 cm.) and close together. 



Forma FARLOWII (Weber) Borgesen, 1907, p. 365 ; C. plu- 

 maris forma Farlowii Weber, 1898, p. 295. Pinnules opposite, 

 alternate, in pairs, or even in several rows. 



TO. C. LYCOPODIUM Harvey, 1858, p. 19, PI. XXXVII. B ; 

 Weber, 1898, p. 304; C. lanuginosa Alg. Am-Bor. , No. 37. 

 Stolon and base of fronds covered with woolly hairs ; frond 

 up to 10 cm. high ; from the point where the hairs cease, cov- 

 ered with simple, bristle-like, imbricate, serrate ramuli, ending 

 sharply in a mucro ; branches of the middle of the frond longer 

 than those nearer the base or the summit. Fla., W. I. 



Var. DELICATULA (Grun.) Weber, 1898, p. 305, PI. XXV, 

 fig. 2. Plant very slender, not over 3 cm. high ; ramuli fili- 

 form, erect, slightly acuminate. Fla. Pacific, Australia. 



This seems to be merely a dwarf form, but it is of interest as 

 occurring both at Florida and on the opposite side of the, globe, 

 while the type occurs only in Florida. 



ii. C. FREYCINETII Agardh, 1822, p. 446; Weber, 1898, 

 p. 310, PI. XXV, figs. 4-1 1 ; XXVI, figs. 1-6; Phyk. Univ., 

 No. 326. Stolon usually stout, creeping, naked ; frond cylin- 

 drical or compressed at the base, then plane, linear, foliaceous, 

 often spirally twisted, often alternately constricted and widened, 

 branching always dichotomous, margin dentate, serrate, or 

 entire. 



As indicated by this description, this species varies greatly, 



