Petrophytum caespitosum subsp. caespitosum

Illustrated
Synonyms: Petrophytum caespitosum var. elatius (S. Watson) Tidestrom P. elatius Nuttall Spiraea caespitosa var. elatius S. Watson
Treatment appears in FNA Volume 9. Treatment on page 413. Mentioned on page 411.

Short-shoots usually compressed into tight rosettes, sometimes internodes extended and rosette structure lost. Leaf-blades 0.4–1.4 cm, abaxial surface pilose to sericeous. Inflorescences compressed panicles, proximal 1/2 of panicle varying from unbranched with scattered bracts along peduncles to ± branched with branches 1–3 (–4+) cm, distal 1/2 of panicle often appearing racemose with no or relatively few branches. Flowers: petal apex obtuse to slightly cleft.


Phenology: Flowering May–Oct.
Habitat: Dry rock ledges, rocky outcrops, talus slopes
Elevation: 1100–3000 m

Distribution

V9 698-distribution-map.jpg

Ariz., Calif., Colo., Idaho, Mont., Nev., N.Mex., S.Dak., Tex., Utah, Wash., Mexico (Coahuila), Mexico (Tamaulipas)

Discussion

Subspecies caespitosum is frequently found with relatively small leaves that are pilose to densely sericeous. Sometimes plants growing in moister conditions will have larger leaves and reduced indument, and they may develop visible primary and secondary venation.

For this treatment, var. elatius has been subsumed in subsp. caespitosum, as the author is uncertain as to whether it should be recognized as a variety within this subspecies or merits elevation to subspecies status. Variety elatius has short shoots with extended internodes (1–3 cm), larger panicles (10–20 × 8–15 cm), widely branched with 4–10 cm branches, with bracteoles linear to narrowly oblanceolate, 8–16 mm; it is found on dry rock ledges and outcrops, often on limestone, between 1100 and 2800 m in Arizona, Nevada, and Utah.

Variety elatius appears to intergrade with subsp. caespitosum (freely intergrades; T. H. Kearney and R. H. Peebles 1942, 1960) but does not appear to be merely an ecological variant of it. Morphological work on the carpel of Petrophytum by C. Sterling (1966) indicated that, for the carpel characters examined, the character state distribution of P. elatius (here cited as var. elatius) was most similar to that of P. hendersonii. Variety elatius was dissimilar to both P. caespitosum (infraspecific taxon not identified, most likely subsp. caespitosum) and P. cinerascens. If var. elatius was only an ecological variant of P. caespitosum, it would be expected that carpel morphology and anatomy would be more similar than found by Sterling. Variety elatius may merit taxonomic recognition.

Selected References

None.

Lower Taxa

None.

"dm" is not declared as a valid unit of measurement for this property.

pilose +  and sericeous +
Richard Lis +
(Nuttall) Rydberg +
gray +, brown +  and dark-brown +
compound +  and simple +
opposite +  and alternate +
Spiraea caespitosa +
0.4 cm4 mm <br />0.004 m <br /> (1.4 cm14 mm <br />0.014 m <br />) +
1(-3)-veined +
2.5 cm25 mm <br />0.025 m <br /> (3 cm30 mm <br />0.03 m <br />) +
0.4 cm4 mm <br />0.004 m <br /> (1.8 cm18 mm <br />0.018 m <br />) +
spatulate +
0.2 cm2 mm <br />0.002 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
0.2cm +  and 0.4cm +
pilose +  and sericeous +
subulate +  and narrowly obtrullate +
3mm +  and 8mm +
3 cm30 mm <br />0.03 m <br /> (4 cm40 mm <br />0.04 m <br />) +
few +  and no +
hirsute +  and pilose +
Ariz. +, Calif. +, Colo. +, Idaho +, Mont. +, Nev. +, N.Mex. +, S.Dak. +, Tex. +, Utah +, Wash. +, Mexico (Coahuila) +  and Mexico (Tamaulipas) +
not +  and aggregated +
1100–3000 m +
0.3 cm3 mm <br />0.003 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
canescent +  and sericeous +
unisexual +  and bisexual +
2 cm20 mm <br />0.02 m <br /> (?) +
pilose +, glabrate +  and glabrous +
lanceoloid +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
coriaceous +
not +  and aggregated +
not +  and aggregated +
Dry rock ledges, rocky outcrops, talus slopes +
1 cm10 mm <br />0.01 m <br /> (?) +
crassinucellate +
0.1 cm1 mm <br />0.001 m <br /> (1 cm10 mm <br />0.01 m <br />) +
compound +  and simple +
marcescent +
persistent +
entire +  and crenulate +
inferior +  and superior +
biseriate +  and clustered +
collateral +  and apical +
3 +  and 2 +
branched to compact +  and branched +
15 cm150 mm <br />0.15 m <br /> (20 cm200 mm <br />0.2 m <br />) +
1cm +  and 15cm +
compressed +
0.5 cm5 mm <br />0.005 m <br /> (6 cm60 mm <br />0.06 m <br />) +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
0 (?) +  and 4 (?) +
persistent +
free +  and distinct +
0.1 cm1 mm <br />0.001 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
Flowering May–Oct. +
adnate +, free +, connate +  and distinct +
Mem. New York Bot. Gard. +
not arillate +
list;count +
persistent +
free +  and distinct +
ovatelanceolate +
0.1 cm1 mm <br />0.001 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
Illustrated +
free +  and distinct +
1.5-2(-2.5) times petals +
branched +  and simple +
intertwined +
coalesced +
decumbent +  and prostrate +
ascending +  and erect +
0.2 cm2 mm <br />0.002 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
persistent +  and deciduous +
distinct +
basal +, lateral +, subterminal +  and terminal +
not elongate +
sericeous +, pilose +, canescent +, strigose +  and glabrate +
Petrophytum caespitosum var. elatius +, P. elatius +  and Spiraea caespitosa var. elatius +
Petrophytum caespitosum subsp. caespitosum +
Petrophytum caespitosum +
subspecies +
inconspicuous +
thickened +  and minute +