Flora of North America species comparison

Varieties 2 (2 in the flora).

Characters useful in recognizing specimens of Geum macrophyllum are yellow petals, epicalyx bractlets often absent, proximal style segment sparsely to densely stipitate-glandular, and fruiting receptacles puberulent. Across its broad North American range from Alaska to California and Nova Scotia, G. macrophyllum exhibits considerable variation. Based largely on the shape of the terminal leaflet of the basal leaves and the degree of dissection and shape of the divisions of the distal cauline leaves, P. A. Rydberg (1913b) distinguished three species within the range of variation treated here as one species. Basal leaves of G. macrophyllum in the strict sense (var. macrophyllum in this treatment) have relatively large reniform to rounded terminal leaflets and the distal cauline leaves are three-cleft into rhombic or cuneate lobes. The basal-leaf terminal leaflets of G. perincisum (= var. perincisum) are only slightly larger than the laterals and are deeply lobed into rhombic-obovate segments; the distal cauline leaves are dissected into oblanceolate divisions. Both basal and cauline leaves of G. oregonense (= var. perincisum) are intermediate between those of G. macrophyllum and G. perincisum. W. Gajewski (1955) crossed all three taxa under discussion and examined leaf morphology and cytology of the F1 and F2 hybrids. He concluded that they were distinct but not yet completely separated species. Fairly well correlated with the more dissected leaves of G. oregonense and G. perincisum is the presence of minute stalked glands on the pedicels. The treatment here follows H. M. Raup (1931) in recognizing two varieties of G. macrophyllum based more on pedicel glandularity than leaf morphology.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Of conservation concern.

Geum schofieldii is one of the more attractive yet seldom seen species of avens in North America; it is known from the rocky wet mountains of the Queen Charlotte Islands and northern Vancouver Island.

Because Geum schofieldii appears to be intermediate morphologically between G. calthifolium and G. rossii, some botanists have considered it to be a hybrid and included it in synonymy with G. ×macranthum [G. calthifolium × G. rossii]. The 16-ploid chromosome number (2n = 112) of G. schofieldii suggests an allopolyploid origin. Geum rossii is not known to occur in the Queen Charlotte Islands or on Vancouver Island; the plants cannot be of recent hybrid origin. Geum ×macranthum is found in the Aleutian Islands and the Alaska Peninsula where the two parental species overlap. Compared to G. schofieldii, its leaves are more pinnate than lyrate-pinnate, with 9 to 13 major leaflets instead of 5 to 7. Also, G. ×macranthum appears to be sterile; G. schofieldii appears to be fertile, suggesting that the latter is a valid species. The distinctness of G. schofieldii pollen also supports its specific status (R. J. Hebda and C. C. Chinnappa 1990).

(Discussion copyrighted by Flora of North America; reprinted with permission.)