Euphrasia subarctica

Stems simple, sometimes branched, to 30 cm; branches 1 or 2 pairs, erect, from distal cauline nodes; cauline internode lengths (1–)2–5 times subtending leaves. Leaves: blade oblanceolate to broadly ovate, 2–6(–11) mm, margins crenate, teeth 1–3(–5) pairs, apices obtuse to subacute. Inflorescences sparsely spicate, not 4-angled, beginning at node 3 or 4(–6); proximal internode lengths 0.8–3(–4) times bracts; bracts green, often purplish adaxially, broader than leaves, ovate to obovate, length not more than 2 times width, 3–10 mm, base cuneate, surfaces sparsely hirsute and hairs eglandular or +/- densely, sometimes sparsely, glandular-pilose and hairs glandular, stalks sometimes flexuous, 3–6-celled, 0.2–0.6 mm, teeth 2–6 pairs, longer than wide, apices subacute to acute, rarely aristate, sinuses between teeth acute. Flowers: calyx lobes straight, apex acute; corolla white to yellow, seldom with violet veins, 3–4 mm, lips +/- equal. Capsules elliptic to oblong, (2.5–)5–6.5 mm, apex truncate to retuse.

Phenology: Flowering summer.
Habitat: Sandy, gravelly, or damp grassy places, stream banks, shores, thickets, heathlands, tundra.
Elevation: 0–2500 m.

Alta., B.C., Man., N.W.T., Sask., Yukon, Alaska, Mont.

Discussion

The holotype (Raup & Abbe 4633, GH) fixes the name Euphrasia subarctica to individuals with long, glandular hairs. Eglandular individuals are sometimes found growing mixed together with typical, glandular E. subarctica in Alaska and northwestern Canada. Similarly, eglandular and long glandular-pubescent individuals are intermixed in populations of otherwise morphologically similar, but not identical, E. disjuncta, including the specimens of its paratype (Fernald & Wiegand 6166, CAN). Due to the clear tendency for the glandular forms to be more frequent in the west, while eglandular ones are more typical in the east, as well as other morphological differences, E. subarctica and E. disjuncta are treated as separate species here. However, it is likely that they represent a single lineage with a disjunct distribution, which could be a result of postglacial colonization from two separate refugia in western and eastern North America. Co-occurrence of glandular and eglandular states is documented in other diploids [for example, E. picta Wimmer in the Austrian Alps (P. F. Yeo 1978)]. Occasional individuals of E. subarctica with yellow corollas may be the result of introgression from E. mollis.

Selected References

None.

Lower Taxa