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. EUROPÀEUM. 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 pinnæ 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.
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.)]
_Trichómanes Boschiànum. Trichómanes rádicans_
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 Pinnules of Filmy Fern (From Waters's "Ferns." Henry Holt & Co.)]
[Illustration: Fiddleheads or Crosiers of Christmas Fern]
[The works of these authors are listed under "Fern Literature" in the following pages.]
EATON, DANIEL CADY. Born at Gratiot, Mich., September 12, 1834. His grandfather was Amos Eaton, noted botanist and author. Studied botany under his friend, Prof. Asa Gray, who had studied with Prof. John Torrey, who in turn was a pupil of Amos Eaton. Daniel C. was professor of botany in Yale College, for more than thirty years. A man of graceful and winsome personality, an authority on ferns, and widely known by his writings. His masterpiece was "The Ferns of North America" in two large, quarto volumes, beautifully illustrated. He died June 29, 1895.