Purshia tridentata var. tridentata

IllustratedEndemic
Treatment appears in FNA Volume 9. Treatment on page 340. Mentioned on page 341.

Stems: young long-shoots arachnoid-villous to pubescent curved hairs 0.1–0.4 mm, stipitate-glandular or not. Leaves dimorphic, long-shoot and most short-shoot leaves summer–winter deciduous; blade flabelliform, thin, margins weakly revolute, usually 3-toothed, sometimes 3-lobed, apically, not punctate or rarely with sessile or stipitate-glands but these not strongly resinous, abaxial surface white arachnoid-villous to arachnoid-tomentose, adaxial persistently arachnoid-villous (hairs crinkled) and hirtellous; late-season short-shoot and sometimes first-formed (proximalmost) spring short-shoot leaves winter-persistent, remaining at base of new season’s growth, smaller, thick, 3-lobed distally, margins with or without resinous punctate glands, glabrous or hirtellous. 2n = 18.


Phenology: Flowering Mar–Jun(–Jul).
Habitat: Mostly well-drained alluvial plains, sagebrush scrub, grasslands, pinyon-juniper woodlands, yellow pine, red fir forests, subalpine zones
Elevation: (60–)1000–2500(–3400) m

Distribution

V9 558-distribution-map.jpg

B.C., Ariz., Calif., Colo., Idaho, Mont., Nebr., Nev., N.Mex., Oreg., Utah, Wash., Wyo.

Discussion

Plants of var. tridentata have dimorphic leaves. Short shoots typically produce thick glandular-margined, overwintering leaves in the later summer (and sometimes in early spring) and thinner, flabelliform winter-deciduous leaves in spring and summer or only on long shoots. Variation in persistent and deciduous leaves occurs through the range, with northern plants producing mostly thinner deciduous leaves and plants in more arid zones to the south producing more thick, persistent and fewer thin, deciduous leaves. At high elevations in the White Mountains of Inyo County, California, low vegetative plants have only thick, persistent leaves as in var. glandulosa, except that long-shoot leaves are of the thin, deciduous type characteristic of var. tridentata. In more arid regions plants produce only thick, persistent leaves on both long and short shoots, characteristic of var. glandulosa with a broad zone of transition between the taxa. The persistent leaves provide important, high-protein winter browse for ungulates. Development of stipitate glands on stems, leaves, and hypanthia is highly variable even within populations.

Selected References

None.

Lower Taxa

None.
arachnoid-villous +  and arachnoid-tomentose +
0.7 cm7 mm <br />0.007 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
obovoid-fusiform +
3.5mm +  and 5.2mm +
hirtellous +  and arachnoid-villous +
James Henrickson +
(Pursh) de Candolle +
gray +  and cinnamon brown +
weathering +
compound +  and simple +
opposite +  and alternate +
cuneate +  and clawed +
Tigarea tridentata +
1.5 cm15 mm <br />0.015 m <br /> (1.9 cm19 mm <br />0.019 m <br />) +
0.1 cm1 mm <br />0.001 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
persistent +
0.4 cm4 mm <br />0.004 m <br /> (0.9 cm9 mm <br />0.009 m <br />) +
flabelliform +
0.3 cm3 mm <br />0.003 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
free +  and distinct +
ascending +  and deflexed +
B.C. +, Ariz. +, Calif. +, Colo. +, Idaho +, Mont. +, Nebr. +, Nev. +, N.Mex. +, Oreg. +, Utah +, Wash. +  and Wyo. +
not +  and aggregated +
(60–)1000–2500(–3400) m +
nectariferous +
glabrous +, not +, stipitate-glandular +  and villous +
1 cm10 mm <br />0.01 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
unisexual +  and bisexual +
not +  and aggregated +
oblanceoloid +  and obovoid-fusiform +
0.4 cm4 mm <br />0.004 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
Mostly well-drained alluvial plains, sagebrush scrub, grasslands, pinyon-juniper woodlands, yellow pine, red fir forests, subalpine zones +
not +  and stipitate-glandular +
0.01 cm0.1 mm <br />1.0e-4 m <br /> (0.04 cm0.4 mm <br />4.0e-4 m <br />) +
0.35 cm3.5 mm <br />0.0035 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
stipitate-glandular +  and pubescent-sericeous +
0.25 cm2.5 mm <br />0.0025 m <br /> (0.65 cm6.5 mm <br />0.0065 m <br />) +
crassinucellate +
green-gray +
deciduous +
6mm +  and 15mm +
immature +  and abscising +
flabelliform +
0.3 cm3 mm <br />0.003 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
rarely +  and punctate +
hirtellous +  and glabrous +
3-lobed +  and 3-toothed +
hirtellous +, glabrate +  and glabrous +
inferior +  and superior +
clustered +, biseriate +  and superposed +
0.02 cm0.2 mm <br />2.0e-4 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
0 (?) +  and 4 (?) +
free +  and distinct +
0.4 cm4 mm <br />0.004 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
Flowering Mar–Jun(–Jul). +
adnate +, free +, connate +  and distinct +
Trans. Linn. Soc. London +
not arillate +
persistent +
free +  and distinct +
spreading-reflexing +  and spreading-reflexed +
ovate +  and oblong-ovate +
winter-persistent +  and deciduous +
spring +  and summer-winter +
branched +  and simple +
2 cm20 mm <br />0.02 m <br /> (6 cm60 mm <br />0.06 m <br />) +
0.5 cm5 mm <br />0.005 m <br /> (2 cm20 mm <br />0.02 m <br />) +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
Illustrated +  and Endemic +
free +  and distinct +
3 +  and 20 +
adnate +  and free +
0.7 cm7 mm <br />0.007 m <br /> (1 cm10 mm <br />0.01 m <br />) +
persistent +
distinct +
basal +, lateral +, subterminal +  and terminal +
elongate +
0.5 cm5 mm <br />0.005 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
Cowania +
Purshia tridentata var. tridentata +
Purshia tridentata +
variety +
inconspicuous +
hemispheric +
summer-winter-deciduous +  and evergreen +
not +, stipitate-glandular +, glabrous +, hirtellous +  and arachnoid-villous +
0.4 cm4 mm <br />0.004 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +