Festuca of North America

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S. G. Aiken, M. J. Dallwitz, C. L. McJannet, and L. L. Consaul

Festuca saximontana subsp. purpusiana (St.-Yves) Tzvelev

Nomenclature

Bot. Zh. (Leningr.) 56: 1254. 1971. F. ovina subsp. saximontana var. purpusiana St.-Yves, Candollea 2: 247. 1925. F. purpusiana Tzvelev, Zalki SSSR (Poaceae URSS): 406. 1976. Type: U.S.A. California: Mountains north of Farewell Gap, elev. 11–12,000 ft. April-Sept. 1897, C.A. Purpus 5112, pro parte. GH! Topotype: C.A. Purpus 3076 US!

F. ovina var. supina sensu Piper, Contrib. U.S. Natl. Herb. 10: 27. 1906, non (Hack.) Schur, Bot. Centralb. 8: 405. 1881.

F. supina sensu Rydb., Fl. of Rocky Mountains: 86. 1917, non Schur, Enum. Fl. Transsilv. 784. 1866.

F. saximontana var. purpusiana (St.-Yves) Frederiksen & Pavlick in Frederiksen, Nord. J. Bot. 2: 534. 1983. Type: U.S.A. Oregon: Wallowa Mt., near lake, 2 August 1900, Cusick 2454. Lectotype: GH. (Frederiksen 1982).

Habit. Plants bluish gray green (variable), 5–25 cm high, densely tufted (sometimes forming dense, tightly grouped clumps), tiller bases stiffly erect, bases not purplish, horizontal rooting stems absent. Vegetative shoots arising from within existing sheaths.

Vegetative morphology. Sheaths glabrous, conspicuous at the base of the plant, persisting for more than 1 year (more conspicuous than is usual in F. brachyphylla subsp. coloradensis Frederiksen), remaining entire, not conspicuously splitting between the veins, open more than half their length. Collars glabrous. Auricles represented by distinct, erect, swellings. Auricular cilia absent. Ligules 0.2–0.5 mm long, ciliate. Leaf blades 2–6.5 cm long, erect, stiffish (especially in short plants from arid habitats). Adaxial blade surfaces with trichomes, abaxial blade surfaces glabrous. Leaf blades plicate; 0.3–0.4–0.5 mm wide, 0.55–0.65–0.8 mm deep. Veins 5. Adaxial to abaxial sclerenchyma strands absent. Abaxial sclerenchyma poorly developed or well developed, in broad bands or continuous. Ribs 1 (well defined, 2–4 poorly defined). Uppermost culm leaf sheaths not inflated. Flag leaf blades 1–2.5 cm long. Culm nodes never exposed (usually) or becoming exposed (rarely), 1 (where applicable); internodes glabrous.

Floral morphology. Inflorescence 1–5 cm long. Inflorescence branches at the lowest node 1–2, appressed after anthesis, 0.5–1.2 cm long. Rachis angular in cross section, trichomes mainly on the ridges or trichomes over the entire surface. Spikelets aggregated towards the ends of the branches; 1–4(–5) on the longest branches; (4.8–)5.5–6.5(–7.6) mm long, 1.5–3 mm wide. Proliferating spikelets absent. Florets 2–5. Glumes unequal, with trichomes, vestiture at the apex only (sometimes sparse), margins ciliate. First glume 2–3.4 mm long, veins 1. Second glume shorter than the first lemma, 3–4.8 mm long, veins 3. Rachilla internodes antrorsely scabrous (scaberulous). Lemma callus not elongated. Lemma 3.6–5.6 mm long, nerveless in dorsal view or sometimes with only the centre vein distinct, with trichomes (scaberulous), trichomes on the upper portion only (and down the central vein, but elsewhere glabrous); apex entire. Lemma awn 0.8–1.8 mm long. Palea 3.6–4.7 mm long, distinctly pubescent between the keels. Lodicules with marginal teeth, glabrous, 0.6–1.4 mm long. Anthers 1.5–1.8 mm long. Ovary apex glabrous. Caryopsis 2–2.5 mm long.

Cytology. 2n = 42 (Frederiksen (1982) cult SF 774, seeds originating from Bitteroot Mountains, Montana).

Habitat and Distribution. Native; alpine. Northwestern USA: Oreg., Wash.; Southwestern USA: Calif., Nev.; Rocky Mountains USA: Colo., Utah.

Classification. Subg. Festuca L.

Notes

The descriptive data are based on specimens from alpine regions of Oregon and California. Seed protein data suggested that F. saximontana subsp. purpusiana is distinct from short forms of F. saximontana Rydb. subsp. saximontana (Aiken et al. 1992). In that study, the protein profile determined by SDS-PAGE analyses of F. saximontana subsp. purpusiana seed obtained from the White Mountains of California was compared with the profiles of samples of subsp. saximontana and F. brachyphylla Schult. & Schult. f. obtained from across Canada. The profile of the subsp. purpusiana lacked a heavily stained band that was present in six samples of subsp. saximontana from widely separated areas in North America. Instead the profile of subsp. purpusiana had two narrow bands more similar to those that were found in the same position on F. brachyphylla profiles. The seed protein results might have suggested recognition of F. brachyphylla subsp. purpusiana, but the morphological characteristics of anther lengths and sclerenchyma deposition in leaf cross sections are more similar to F. saximontana subsp. saximontana.

Festuca brachyphylla subsp. coloradensis (=F. brachyphylla subsp. breviculmis) plants were growing in association with F. saximontana subsp. purpusiana at a White Mountain site in California. They were visibly much shorter, more compact, and at a different stage of flowering (photographs in the image library). It is suggested that F. saximontana subsp. purpusiana, like F. brachyphylla subsp. coloradensis has evolved at high altitudes and in relative isolation in the south western United States (Aiken et al. 1992). As both subsp. saximontana and subsp. purpusiana have 2n=42 chromosomes, they are more likely to be able to hybridize if they grow together. It is suspected from herbarium label data that the two subspecies are separated by altitude differences in many locations, with subsp. saximontana in dry grasslands below a forest zone and subsp. purpusiana isolated on the tops of mountains above 3000 m, but this needs more research.

The confusion is reflected in the literature. Tzvelev (1976) indicated that the taxon is known from Chukotsk Peninsula in Asia, an extension that corresponds well with the extension of other Beringian plants, and he recognized F. purpusiana (St.-Yves) Tzvelev. Alexeev (1985) stated that, in North America, subsp. purpusiana is an ecological response of F. saximontana where less sclerenchyma forms in the leaves and refers the Asian material of F. purpusiana sensu Tzvelev to F. brachyphylla.

Frederiksen (1982) based the name F. saximontana var. purpusiana on the Cusick 2454 type, collected in mountains of eastern Oregon, and made the combination in collaboration with L.E. Pavlick. She suggested that the two varieties deviate in (a) the length of the culm, which is distinctly shorter in the taxon she recognized as var. purpusiana and (b) the length of the culms relative to the length of the blades (culms are about twice the length of the blades in "var." purpusiana and more than twice the length of the blades in var. saximontana). The first author has found these characters to be very variable, both on herbarium specimens and in the course of field work. Frederiksen's observations, based on a few specimens only, were that the leaf sheath is never fused more than 1/3 in var. saximontana, while it is fused 1/2 or more in var. purpusiana. Frederiksen concluded that although there seems to be real differences between the taxa concerning the fusion of the leaf sheaths, there are difficulties in distinguishing between them.

The only two diagnostic characters given by St.-Yves (1925) are the colour of the spikelets (normally green or reddish in subsp. saximontana and mostly green variegated, with purple in subsp. purpusiana) and the fusion of the leaf sheath (at most 1/4 fused in subsp. saximontana, 1/3–1/2 fused in subsp. purpusiana). Some authors have emphasized the amount of sheath closure as a taxonomic character in separating the segregated taxa subsp. saximontana, subsp. purpusiana, var. robertsiana Pavlick, and F. canadensis E. B. Alexeev (Alexeev 1983, Frederiksen 1982).

During development a "split ring" develops in the sheaths of subsp. saximontana (Aiken and Darbyshire 1990, illustrated in the image library) It is suspected that the rate of growth of the new shoot coming up through the sheath may influence how rapidly this split opens. The first author's experience and that of Pils (1985), is that this feature is highly variable in most fescues. It can be difficult to determine the difference between 1/4, 1/3, or 1/2 sheath closure in arctic or alpine species that have short sheaths. Lui and Dengler (1992), in an anatomical study, found that the early stages of development of the closed sheaths of F. rubra s.l. and the open sheaths of F. trachyphylla (Hack.) Krajina had many similarities. The work of these authors appeared to imply that differences in sheath development between closely related taxa may be difficult to detect, if plants are grown under uniform conditions, that is, the character, degree of sheath opening, may have a phenotypic component.

Aiken and Darbyshire (1990) also noted that a number of collections of F. saximontana from subalpine and alpine habitats of southern Alberta and British Columbia retained their small stature and dense tufts under uniform cultivation in Ottawa. The variety recognized by Pavlick (1984), i.e. var. robertsiana, described from the Rocky Mountains of British Columbia, is intermediate in culm length between the taxa recognized by Frederiksen (1982) as var. saximontana and var. purpusiana and is placed into synonymy with F. saximontana.

Illustrations

• Habitat and plant. Habitat and plant of F. saximontana subsp. purpusiana. Left, White Mountains of California at approximately 3800 m (at arrow). At 100–200 m below the summit, F. brachyphylla subsp. coloradensis (upper right) and F. saximontana subsp. purpusiana (lower right), grow within meters of each other. • Leaf anatomy. Leaf cross section of F. saximontana subsp. purpusiana. Leaf blades are 0.3–0.4–0.5 mm wide and 0.55–0.65–0.8 mm deep, with 5 veins. Adaxial to abaxial sclerenchyma strands are absent. Abaxial sclerenchyma are poorly developed or well developed, in broad bands or continuous. There is one well defined rib and 2–4 poorly defined ribs. • Cotype specimen: GH. Second specimen of F. saximontana subsp. purpusiana cited by St.-Yves (1925), cotype. Flora of South-Eastern California, Mountains north of Farewell Gap, Alt. 11–12000 ft., April-Sept. 1897, C.A. Purpus 5112. • Distribution map


The interactive key provides access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting specified attributes, and summaries of attributes within groups of taxa.

Cite this publication as: ‘Aiken, S.G., Dallwitz, M.J., McJannet, C.L. and Consaul, L.L. 1996 onwards. Festuca of North America: descriptions, illustrations, identification, and information retrieval. Version: 19th October 2005. http://delta-intkey.com’. Aiken, Dallwitz, McJannet, and Consaul (1997) should also be cited (see References).

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