196 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
forma obtusilobata (Schkuhr) Gilbert. — Washington (C. S. 
Lewis); Lenox; New Marlboro. 
PELLAEA. Cliff Bu.\ke. 
P. atropurpurea (L.) Link. Purple Cliff Brake. — Limestone 
ledges; occasional. 
POLYPODIUM. Polypody. 
P. vulgare L. Common Polypody. — Shaded rocks, chiefly on 
schist, but occasionally on limestone; common. 
forma attenuatum (Milde) Gilbert. — Rich woods; occasional. 
Becket (C. S. Lewis); South Mountain, Pittsfield; Bash Bish Falls, 
Mt. Washington. 
forma auritum (Willd.), comb. nov. — (P. vulgare aurituni Willd. 
Sp. PI. 5: 173, 1810.) 
Becket (C. S. Lewis). 
POLYSTICHUM. 
P. acrostichoides (Michx.) Schott. Christmas Fern. — Rocky 
woods; common. A plant from Lee has the frond subdivided at the 
tip, so that there are four separate tips, the two longest 10 cm. in length. 
forma incisum (Gray) Gilbert. — (var. Schiveinitzii Man. ed. 7 
and 111. Fl. ed. 2; vid. Rhodora, 11: 35, 1909.) 
Occasional with the type. Williamstown; Florida; Washington 
and Becket (C. S. Lewis); Lenox; Stockbridge; Great Barrington. 
A plant collected by Walters in Lanesboro has broad obtuse and in- 
cised pinnae of the year, while the fronds of the year before are normal. 
P. Braunii (Spenner) Fee. — On the margins of cold mountain 
brooks, on Greylock and on Fife Brook, Florida. Two plants in rich 
leaf mould, South Mountain, Pittsfield (S. W. Bailey). These are the 
only known stations for this northern fern in Massachusetts. 
PTERETIS. 
{Maiteuccia 111. Fl. ed. 2; Onoclea Man. ed. 7; rid. Rhodora, 21: 175, 1919.) 
P. nodulosa (Michx.) Nieuwl. Ostrich Fern. — {M. Struthiop- 
teris 111. Fl. ed. 2; 0. Struthiopteris Man. ed. 7.) 
