Tuckerman's Quillwort

Isoëtes tuckermanii may be an allotetraploid like I. riparia, but it appears to have had different parental species. Variation may also have resulted from multiple allotetraploid origins. Typical plants of I. tuckermanii have thin, soft leaves. More northern plants, referred to as I. tuckermanii var. borealis A. A. Eaton, have thick, stiff leaves.

Isoëtes tuckermanii hybridizes with I. echinospora; I. engelmannii [ = I. x foveolata A. A. Eaton ex Dodge]; and I. lacustris [ = I. x harveyi A. A. Eaton].

Plants aquatic, occasionally emergent. Rootstock nearly globose 2(--3)-lobed. Leaves evergreen, olive green to reddish brown, pale toward base, spirally arranged, to 20 cm, pliant to rigid, gradually tapering to tip. Velum covering less than 1/2 of sporangium. Sporangium wall brown-streaked. Megaspores white, 450--650 μm diam., reticulate with ridges having irregular and roughened crests; girdle densely papillate. Microspores gray in mass, 25--35 μm, spinulose. 2n = 44.

Spores mature in late summer. Slightly acid lakes, ponds, and streams; N.B., Nfld., N.S., Ont., Que.; Conn., Maine, Mass., N.H., N.J., N.Y., R.I., Vt.

Isoetes acadiensis, the Acadian quillwort is a species of quillwort in the Isoetaceae family described by Kott in 1981. It can be found along the shores of lakes, ponds, and rivers in Newfoundland, Nova Scotia, and New Brunswick, as well as in the American states Maine, Massachusetts, and New Hampshire. It has a similar distribution to that of I. tuckermanii. It bears 9 to 35 mostly recurved leaves, each 5–21 cm long. The leaves are usually dark green, though can occasionally be tinged with red. The sporangium can be up to five millimeters long and 3 millimeters in length, covered one sixth to one third by the velum. The spherical megaspores are 400-570 micrometers in diameter, and bear smooth ridges. The kidney shaped microspores are 25 to 30 micrometers long. It was originally believed to be a member of Isoetes hieroglyphica because of their similar megaspore structure.