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Blunt-lobed Grapefern

Botrychium oneidense (Gilbert) House

Family Ophioglossaceae

Description

Botrychium oneidense is very similar to B. dissectum forma obliquum and to B. multifidum. The principle differences are in the cutting of the pinnae. In B. dissectum forma obliquum and B. multifidum pinnae are cut into numerous pinnules (which may also be lobed slightly). In B. oneidense pinnae are not cut or lobed or only scarcely so, and the pinnules are broad, obliquely ovate, and blunt-tipped. In B. d. forma obliquum they are narrow, sometimes broad, obliquely trowel-shaped or linear, and pointed at the tips. The pinnae of B. oneidense are toothed marginally which is also the case for B. d. forma obliquum and some forms of B. multifidum. The toothing of pinnae and pinnule margins in B. oneidense is inconspicuous, shallow and regular while in B. d. forma dissectum it is conspicuous and irregular. Marginal toothing in B. multifidum is inconspicuous, shallow, and somewhat regular. Frond coloration of B. oneidense is dark green to bluish-green even in the fall. B. dissectum very frequently becomes bronze-colored in the late fall as temperatures drop. B. multifidum is variable in coloration changes as cold weather approaches but it usually is green.

Phenology is another characteristic helpful in determining species. B. oneidense, B. multifidum, B. rugulosum, and B. dissectum are semi-evergreen. In the early spring the frond of the previous season is still alive but a new frond is slowly emerging. It is in frond pigmentation that differences between species can be seen. The young folded leaves of B. rugulosum and B. dissectum are brilliant pale red of scarlet, while B. oneidense and B. multifidum are pale green. Sporangial maturation also is consistent with species and follows a definite order: B. multifidum, B. oneidense, B. rugulosum, and finally B. dissectum. Of course, this assumes all four species are growing in the same vicinity or in close enough proximity to enable observation.

Habitat

Typically found in moist forests especially near wetland edges. B. oneidense also occurs in open areas with adequate moisture.

Status

MN – Endangered

WI – Special Concern

To my knowledge, B. oneidense has not been found in northeastern Minnesota but it does occur west and south of the region. Specimens from Cook, St. Louis, and Carlton counties have been collected but these are probably B. dissectum and B. multifidum. The specimen shown is B. oneidense and was collected from Itasca County, MN in 1999. It was found in a large colony of B. multifidum and B. dissectum with some B. rugulosum plants in an open, moist field.

More details:
Botrychium ternatum (Thunberg) Swartz var. oneidense Gilbert, Fern Bull. 9: 27. 1901; B. dissectum Sprengel var. oneidense (Gilbert) Farwell; B. multifidum (S.G. Gmelin) Ruprecht var. oneidense (Gilbert) Farwell. Trophophore stalk 2--15 cm, 1.5--2.5 times length of blade rachis; blade dull bluish green, ± plane, 2--3-pinnate, to 15 × 20 cm, ± leathery. Pinnae to 5 pairs, usually remote, horizontal to ascending, distance between 1st and 2d pinnae not or slightly more than between 2d and 3d pairs, undivided except in proximal 2/3--3/4. Pinnules obliquely ovate, margins finely crenulate to denticulate, apex rounded to acute, venation pinnate. Sporophores 2--3-pinnate, 1.5--2.5 times length of trophophore. 2 n =90. Botrychium oneidense commonly occurs with B . dissectum and B . multifidum . Young individuals of both may resemble B . oneidense (W.H. Wagner Jr. 1961b). Leaves green over winter, sporophores seasonal, new leaves appearing in spring. In moist, shady, acidic woods and swamps;

Taxonomic References

Clausen, J. T. 1943. Studies in the Ophioglossaceae. American Fern Journal. 33:11-27.

Lellinger, D. B. 1985. A Field Manual of the Ferns & Fern-Allies of the United States and 

 Canada. Smithsonian Institution Press, Washington, D. C. ix + 389 pages.

Wagner, Jr., W. H. 1960. Periodicity and Pigmentation in Botrychium subg. Sceptridium

 in the Northeastern United States. Bulletin of the Torrey Botanical Club. 87(5):303-325.

Wagner, Jr., W. H. and F. S. Wagner. 1993. OPHIOGLOSSACEAE C. Arardh in Flora of

 North America Editorial Committee. Flora of North America. Vol. 2. Pteridophytes and 

 Gymnosperms. Oxford University Press. New York. xvi + 475 pages.