ard Island, Minnesota, south to Florida and Texas, and north to
Newfoundland and Labrador.

Var. _gracilis_. A form much reduced in size.

Var. LAURENTIANUM. A conspicuous variety having thick and heavy sterile
fronds less finely divided than the type, with the segments crowded to
overlapping. Pinnules shorter than the type, tending to be ovate, outer
segments strongly spatulate. Fertile spike relatively short and stout,
strongly paniculate when well developed. Ultimate segments flat, folaceous,
one mm. wide. Mostly confined to the limestone district near the Gulf of
St. Lawrence, Labrador, Newfoundland, Quebec, Maine, and Michigan.

Var. INTERMEDIUM. Segments of sterile fronds ultimately much spatulate,
previously ovate, not overlapping. Segments of fertile fronds ultimately
narrowly flattened. (For this and the other varieties see Rhodora of
September, 1919.) Nova Scotia, Maine, Vermont, Massachusetts, Connecticut,
northern New York, Illinois, and Missouri.

Var. EUROPAEUM. Fertile frond less finely dissected than in type. Ultimate
segments more obtuse than in type; has but very slight tendency towards the
spatulate form of the two previous varieties. Pinnules lanceolate, strongly
decurrent so that the pinnae are merely pinnatifid. In coniferous forests
of Canada, and confined to calcareous regions. Quebec, New Brunswick, New
Hampshire, Vermont, New York, Ontario, Montana, and British Columbia. Said
to be rare even in Europe.

V

THE FILMY FERN FAMILY

_HYMENOPHYLLACEAE_

The filmy ferns are small, delicate plants with membranaceous, finely
dissected fronds from slender, creeping rootstocks. Sporangia sessile on
a bristle-like receptacle. There are about one hundred species, mostly
tropical, only one of which grows as far north as Kentucky.

[Illustration: Filmy Fern _Trichomanes Boschianum_ (From Waters' "Ferns",
Henry Holt & Co.)]

FILMY FERN. BRISTLE FERN

_Trichomanes Boschianum. Trichomanes radicans_

Rootstocks creeping, filiform, stipes ascending, one to three inches
long, thin, very delicate, pellucid, much divided, oblong-lanceolate,
bipinnatifid. Rachis narrowly winged. Sporangia clustered around the
slender bristle, which is the prolongation of a vein, and surrounded by a
vase-like, slightly two-lipped involucre.

On moist, dripping sandstone cliffs, Kentucky to Alabama. Often called the
"Killarney fern," as it grows about the lakes of Killarney in Ireland.

[Illustration: Fruiting