150 COLLINS A^^) hervey. 



Family DUMONTIACEAE. 

 DuDRESNAYA Bonnemaison. 



1. Peripheral filaments cylindrical or nearly so. 1. D. crassa. 



1. Peripheral filaments distinctly moniUform. 2. 



2. Auxiliary cell terminating the auxiharj' branch. 3. D. caribaea. 



2. Auxiliary cell in middle of auxiliary branch. 2. D. bermudensis. 



1. D. CRASSA Howe, 1905, p. 572, PL XXVIII, XXIX, figs. 12-26; 

 P. B.-A., Nos. 1900, 2196. Castle Harbor, Spanish Point, July, 

 Howe; Castle Harbor, A. E. Wight in Farlow herb.; Salt Kettle, 

 Feb., Buildings Bay, March, Spanish Point, March, Hervey; Shelly 

 Bay, April, Collins. The plants from Buildings Bay, Spanish Point 

 and Shelly Bay were washed ashore; at Salt Kettle, Paget, it grew just 

 below low water mark; at the type station in Castle Harbor it grew 

 at 3 m. depth at low water. It varies much in habit, from the form 

 with short, stout branches, figured by Howe, to forms with slender, 

 acute branches; from generally rounded outline to loosely pyramidal; 

 from forms so dense that when spread out on paper they cover it 

 continuously, without interstices between the branches, to cjuite 

 open specimens, all branches distinct. The largest plant noted was 

 about 25 cm. high and 15 cm. broad. Howe had only cystocarpic 

 plants when describing the species, but we have found antheridia 

 equally abundant, always on separate individuals. The antheridia 

 are formed near the ends of the peripheral filaments, which here bear 

 short, erect lateral branches, usually covered with minute densely 

 branched ramuli of a few cells each, the terminal cell becoming the 

 antheridium. According to the length of the axis and the amount of 

 branching in the ramulus, the antheridia may be cylindrical, conical 

 or ovoid. Sometimes the antheridia are so abundant on the peri- 

 pheral filaments as to form a dense continuous mass, through which it 

 is difficult to see the filaments, except the tips, which project beyond the 

 antheridia. Both antheridial and cystocarpic plants were distributed 

 as P. B.-A., No. 1900. Some forms are habitually not unlike D. caribaea 

 and D. bermudensis, but are easily distinguished microscopically by 

 the character of the peripheral filaments. It is often overgrown with 

 Acrochaetium corymbiferum, and when both have abundant antheridia, 

 it may be perplexing to one unfamiliar with the species. 



2. "d. bermudensis Setchell, 1912, p. 244, PI. XXVII, fig. 8; 

 P. B.-A., No. 2195. Cooper's Island, Feb., Farlow, washed ashore 

 in abundance; St. George's, washed ashore, March, Hervey, 



