198 



short, usually less than one-quarter the height of the plant : 

 spores maturing from July to October (three exceptions)." 

 [Sccpti'idiuai Lyon.) 



The following are included in the key : B. obliqmnn, B. diS- 

 sectiini, B. silaifolhim, B. californicum, B. decompositum, B. 

 Cotilteri, B. Schaffneri, B. Mairicariae, B. piisilliini, B. biter- 

 natmn, B. Jenviani, B. alabaniense, B. Underwoodianiun. 



The above order is probably about as near an approach to a 

 natural order as can be devised for so complex a group. The 

 main divisions are for the most part as indicated in the key which 

 follows : 



Segments more or less deeply lacerate into linear often forking teeth (Vermont, Massa- 

 cliusetts, and Long Island, west to Indiana and south to Virginia and Kentucky). 



2. B. dissectujyi Spreng. 

 Segments entire, crenulate or serrulate, not deeply divided. 



Tips of the penultimate divisions elongate, much larger than the lateral segments 

 (New England to Wisconsin, south to Alabama and Arkansas, also in Jamaica). 



I. B. obliquum Miihl. 

 Tips of the penultimate divisions ovate to deltoid or fan-shaped to reniform, usu- 

 ally about as broad as long, the lateral segments mostly similar in shape and 

 size. 

 Segments mostly acute or acutish (Northern and Western States, Mexico). 

 Plants usually rather large, lamina 7-20 cm. long, 10-30 cm. broad. 

 Lamina stalk usually 5 cm. or more long, plant not excessively 

 fleshy, often very slender. 

 Segments mostly 5-45 mm. long, 2-20 mm. broad, few smaller. 

 Spores maturing from July to September. 



Segments mostly oblong to ovate, margins crenulate 

 or only coarsely serrulate (North Atlantic States 

 and westward, Alaska to California). 



3. B. silail olhim Presl. 

 Segments narrower, cuneiform, oblong or lanceolate, 



outer margins mostly sharply and finely serrulate 

 (Mexico). 4. B. decoviposituvi Mort et Gal. 



Spores maturing from May to June, segments mostly 

 elliptic to rhombic, expanded, plants lax (California). 

 5. B californicuju Underwood. 

 Segments all small, 2-5 mm. long, I— 5 mm. broad (Mexico), 

 6. B. Schaffneri Underwood. 

 Lamina stalk short, I-4 cm. long, plant very stout and fleshy (Mon- 

 tana and Wyoming to Oregon). 7. B, C(9?///^rz' Undervvood. 

 Plants normally smaller, lamina 2-4.5 '^™- long; 3-7 cm. broad. 



Lamina stalk not more than 2 cm. long, plants stout (Mexico). 



8. B. pnsilhim Underwood. 



