Najas gracillima
slender water nymph, thread-leaf water-nymph
slightly branched distally, 4.5–48 cm × 0.2–0.7 mm;
internodes 0.1–3.2 cm, without prickles.
spreading to ascending with age, 0.6–2.8 cm, lax in age;
sheath 0.5–1.5 mm wide, apex truncate;
blade 0.1–0.5 mm wide, margins minutely serrulate, teeth 13–17 per side, apex acute with 2–3 teeth, teeth unicellular;
midvein without prickles abaxially.
1–3 per axil, staminate and pistillate on same plants.
in distal axils, 1.5–2 mm;
involucral beaks 2-lobed, 0.8 mm;
anthers 1-loculed, 1.3 mm.
distal to proximal on plant, 0.5–2.7 mm;
styles 0.3–1.5 mm;
stigmas 2-lobed.
not recurved, light brown, fusiform, 2–3.2 × 0.4–0.7 mm, apex with style situated offat center;
testa dull, 3 cell layers thick, pitted;
aeroleareoles regularly arranged in 40 longitudinal rows, not ladderlike, 4-angled, longer than broad, end walls raised.
= 24, 36.
Najas gracillima
No specimens were seen from in Alberta, Manitoba, or Quebec, but the species is to be expected there.
Najas gracillima is most similar to N. minor, especially in vegetative condition. Najas gracillima, however, can be separated from the latter species by its style arising off-center at the apex of the ovary wall and by its aeroleareoles being longer than broad. Late in the growing season, the leaves of N. minor become recurved; those of N. gracillima do not.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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