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Because of very limited intrageneric differences
in floral morphology and only a few significant fruit differences, characters
of vegetative morphology are particularly important in distinguishing the
various taxa within Arctostaphylos. Characters such as growth
form are quite variable with some taxa, such as A. uva-ursi subsp. cratericola,
being prostrate mat-formers, while others such as A. pungens are
often upright shrubs or small trees. Leaf morphology varies widely,
with size, shape, margin, pubescence, and orientation all being taxonomically
important. The two neotropical taxa are easily distinguished
by the vertically oriented unifacial leaves of A. pungens in contrast
to the horizontally oriented bifacial leaves of A. uva-ursi subsp. cratericola.
Within the Arbuteae, the floral morphology
of Arctostaphylos appears to be advanced, with Comarostaphylis (amongst others) in an intermediate position and Arbutus most primitive
(Palser, 1954). Palser reached these conclusions on the basis of
sepal vascular supply, Arctostaphylos being characterized by a light
supply arising from a single trace in contrast to heavier supplies in the
supposedly more primitive genera. According to Palser (1954), "the stamens
are usually considered not to be epipetalous, but sections show that the
tissues of filament and corolla are often undiverged for a short distance,
particularly in the sepalad whorl, and this is reflected in the fact that
when the corolla is pulled or falls normally from a flower the stamens
go with it." The leaf midrib bundle, often more or less circular in cross-section
(Stevens, 1969), can be used to separate Arctostaphylos from most
other genera of the Arbuteae (e.g., Comarostaphylis) which typically
have elliptic bundles. Carlquist (1985) has found vasicentric tracheids
in all species (nine) of Arctostaphylos studied, as well as in other
genera of the Arbuteae. He interprets these as a type of drought
survival mechanism which functions by maintaining conduction even during
extremely dry periods. This adaptation seems particularly advantageous
for evergreen shrubs in chaparral or other areas of Mediterranean-type
climate.
A number of Arctostaphylos species
are used as ornamental shrubs (Everett, 1964; Schmidt, 1980). Wells
(1993) notes that, while beautiful, many are difficult to cultivate due
to fungi and salinity and alkali conditions. Arctostaphylos uva-ursi is very desirable as a ground cover ornamental.
ARCTOSTAPHYLOS Adanson, Fam. pl. 2: 165, 520.
1763 (nom. cons.); A.P. de Candolle, Prodr. 7: 584-586. 1839;
Klotzsch, Linnaea 24: 78-81 (as Arctostaphylos and Daphnidostaphylis).
1851; Nuttall, Trans. Amer. Philos. Soc. 8: 251 -272 (as Arctostaphylos and Xerobotrys, 266-268). 1843; Abrams in Small, N.
Amer. fl. 29(1): 92-101. 1914; Standley, Trees shrubs Mexico,
Contr. U.S. Natl. Herb. 23(4): 1094-1099. 1924; Jepson, Man.
fl. pl. Calif. 745-751. 1925; Eastwood, Leafl. W. Bot. 1: 197-100.
1934; Jepson, Fl. Calif. 3(1): 29-51. 1939; Adams, J.
Elisha Mitchell Sci. Soc. 56: 1-62. 1940; Abrams, Ill. fl.
Pacific states 309-326. 1951; Munz & Keck, Calif. fl. 416-430.
1959; Munz, Fl. s. Calif. 398-401. 1974; Packer &
Denford, Canad. J. Bot. 52: 743-753. 1974; Roof, Four Seasons
5: 2-24. 1976; Roof, Changing Seasons 1(1): 2-24. 1979,
1(2): 2-32. 1980, 1(3): 2-32. 1980, 1(4): 2-23. 1982;
Wiggins, Fl. Baja Calif. 398-400. 1980; Fromard, Canad. J.
Bot. 65: 687-695. 1987; Diggs & Breckon, in Diggs, Ph.D.
dissertation. 1981; Wells, Madrono
19: 193-224. 1968, 21: 268-273. 1972; Wells, Four Seasons
4: 5-27. 1987; Wells, Madrono 4: 330-341. 1988;
Wells, Four Seasons 8: 46-70. 1990, 9: 44-53. 1992a, 9: 60-69.
1992b; Wells in Hickman, Jepson man. higher pl. Calif. 545-559.
1993; Diggs, Fl. Neotrop. Monogr. 66: 133-145. 1995.
Type species: Arctostaphylos uva-ursi (Linnaeus) K. P. J.
Sprengel (Arbutus uva-ursi Linnaeus) (typ. cons.). Named from
the Greek arktos (bear, or the north) and staphyle (a bunch
of grapes).
Uva ursi Miller, Gard. dict. abr. ed. 4. 1754.
Named from the Latin uva (grape) and ursus (bear).
Uva-ursi [Tournefort] Duhamel, Traite arbres et arbustes 2: 371.
1755.
Uva ursi [Tournefort] Moench, Methodus 470. 1794.
Mairania Necker. Elem. 1: 219. 1790.
Xerobotrys Nuttall Trans. Am. Phil. Soc 8: 267. 1843.
Named from the Greek xeros (dry) and botrys (a cluster of
grapes) in allusion to the nature of the fruit.
Daphnidostaphylis Klotzsch, Linnaea 24: 79. 1851.
Named from the Greek daphne (laurel) and staphle (a bunch
of grapes).
Schizococcus Eastwood, Leafl. West. Bot. 1: 98. 1934. Named from
the Greek schizo (split or cleave) and kokkos (a seed, grain,
or berry), emphasizing the chief generic character.
Prostrate, creeping and mat-forming evergreen
terrestrial shrubs, sometimes rooting along the branches, to erect, spreading
or mounding shrubs (-small trees) to 4(-5) m tall; bark smooth to
slightly fissured, often exfoliating, flaking, peeling, or shredding, the
outer bark sometimes thin and papery, when lost the surface below
quite smooth; indumentum of eglandular and/or glandular trichomes
varying in persistence and distribution. Leaves vertically oriented,
unifacial with stomata on both surfaces, or horizontally oriented on prostrate
branches, bifacial with stomata limited to lower surface; blades
more or less flat, coriaceous, margins entire. Inflorescences terminal,
racemose, with 5-15 flowers; floral bracts present at base of pedicels,
small, to ca. 6 mm long; pedicels bracteolate at base. Flowers
typically 5-merous; calyx continuous with pedicel, much smaller than
corolla at anthesis, drying but persistent in fruit, lobes equal, separate
or slightly imbricate at anthesis; corolla urceolate, white to pink,
lobes short, to ca. 1/5 the length of the corollas, imbricate before anthesis,
glabrous or with sparse trichomes internally; stamens (8-)10, equal,
included; filaments dilated near base, sparsely to moderately
illous; anthers ovoid, laterally compressed, with two dorsal appendages
(spurs) attached opposite the attachment to the filament, dehiscence terminal
to somewhat introrse by two pores/slits to nearly 1/2 as long as the anthers,
attached by the porate end, versatile; ovary superior, smooth, without
papillae, glabrous, sessile on a weakly 10-lobed or ribbed hypogynous disk-like
nectary; placentation axile; ovules solitary in each locule;
style straight, included; stigma ca. same diam. as style, weakly
lobed. Fruit drupaceous, berry-like, oblate-spheroidal or depressed-globose,
smooth, without papillae, glabrous, yellow, orange tan-brown to brown or
red at maturity; nutlets (4-)5-7(-10), separable or irreglarly united,
carinate, corrugate; chromosome number n=13, 2n=26 in neotropical
taxa (Niehaus & Wong, 1971).
Arctostaphylos is a primarily north
temperate genus of perhaps 50-65 species, with two neotropical members
extending south as far as Guatemala.
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