Flora of North America species comparison

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Philadelphus microphyllus

Hydrangeaceae

little leaf mock orange, small-leaf mock orange

hydrangea family, mock-orange family
Habit Shrubs, 5–12(–20) dm. Subshrubs, shrubs, trees, or vines [herbs], evergreen or deciduous.
Stems

copper to reddish brown, stiffly to loosely branched, appressed villous-sericeous, ± strigose, hairs often red-gland based, or glabrous;

epidermis soon or tardily deciduous exposing cortex and striate bundle caps;

bark grayish;

internodes (0.1–)1–2.5(–6) cm; short-shoot spurs not present;

axillary buds hidden in pouches.

Leaves

petiole 1–2(–4) mm;

blade greenish or whitish abaxially, green adaxially, linear-lanceolate, narrowly ovate to ovate, (0.5–)0.8–3(–5.5) × (0.2–)0.3–1.3(–3.3) cm, herbaceous to coriaceous, margins usually entire, rarely sparsely serrulate, plane or revolute upon drying, abaxial surface short sericeous-strigose, or sericeous-villous with longer hairs, or with ascending to erect hairs, sometimes with dense to moderate understory of slender curled hairs, adaxial surface glabrous, glabrate, ± sericeous-strigose, villous, or with erect hairs.

usually opposite, sometimes whorled [alternate], simple;

stipules absent;

petiole present or absent;

blade sometimes palmately lobed, margins entire, serrate, serrulate, dentate, denticulate, or crenate;

venation pinnate or acrodromous (Fendlera, Fendlerella, Philadelphus, Whipplea).
Inflorescences

usually solitary flowers, sometimes 3–5-flowered cymes.

terminal or axillary, cymes, panicles, racemes, or corymbs, or flowers solitary.
Pedicels

0.5–3 mm.

Flowers

hypanthium glabrous, sericeous-strigose basally or throughout, or weakly to densely villous to densely lanate with mixed strigose and villous vestiture, with understory of slender curled hairs;

sepals ovate to lanceolate, (2.5–)4–8.5(–10) × (2.5–)3–4.3(–5) mm, apex acute to acuminate-caudate, abaxial surface glabrous, sericeous-strigose, or weakly to densely villous to densely lanate with mixed strigose and villous vestiture, with understory of slender curled hairs, adaxial surface glabrous except villous along distal margins;

petals white [marked purple near base], oblong-obovate to broadly ovate, (5.8–)7–16(–21) × (5.3–)6–11(–15) mm, margins entire or erose-undulate, apex ± acute, rounded, or notched;

stamens 26–64;

filaments often connivent-connate in irregular clusters in proximal 0.5–4 mm, 1.8–8 mm, of unequal length, glabrous;

anthers yellowish, 0.7–1.2 mm;

styles 4, connate proximally, cylindric, 2.5–5.5(–7) mm, lobes sometimes connate proximally in pairs, 0.5–2.5 mm;

stigmatic surfaces extending from adaxial lobes onto abaxial lobes and down to cylindric style.

bisexual [unisexual], or sometimes marginal ones sterile, radially symmetric (bisexual ones) or bilaterally symmetric with enlarged petaloid sepals (sterile ones);

perianth and androecium nearly hypogynous, perigynous, or epigynous;

hypanthium completely adnate to ovary or adnate to ovary proximally, free distally;

sepals 4–12, distinct or connate basally;

petals 4–12, connate basally [entirely, then calyptrate];

nectary usually present, rarely absent;

stamens 8–200, usually distinct, sometimes connate proximally, free;

anthers dehiscing by longitudinal slits;

pistil 1, 2–12-carpellate, ovary less than 1/2 inferior, 1/2 inferior, or completely inferior, 1–12-locular, placentation usually axile proximally, parietal distally, rarely strictly axile or parietal;

ovules 1–50 per locule, anatropous;

styles 1–12, distinct or connate proximally to most of length;

stigmas (1–)2–12.
Fruits

capsules [berries], dehiscence septicidal, loculicidal, interstylar, or intercostal.
Capsules

oblong-globose or globose-turbinate, (3.6–)5–8(–9.5) × (3.5–)4–7(–9.5) mm, sepals persisting at equator or more distally, capsule distal surface often impressed in 4(–8) radiating lines.

Seeds

short caudate distally, 1.5–2.5 mm.

1–50 per locule, funicular appendage present (Fendlerella, Whipplea) or absent.

Philadelphus microphyllus

Hydrangeaceae
Distribution
from FNA
AZ; CA; CO; NM; NV; TX; UT; WY; Mexico
[WildflowerSearch map]
[BONAP county map]
North America; Mexico; Central America; South America; Eurasia; Pacific Islands
[BONAP county map]
Discussion

Varieties 5 (4 in the flora).

Within Philadelphus microphyllus as treated here, P. A. Rydberg (1905) recognized nine species, C. L. Hitchcock (1943) one species with eight subspecies, and Hu S. Y. (1954–1956) 11 species and four varieties, based on vestiture, leaf size and shape, and floral differences. Four varieties are recognized here within the flora area, with a fifth restricted to Mexico and without the needed varietal combination.

Two characters are particularly important in distinguishing the varieties of Philadelphus microphyllus: adaxial leaf blade cuticle thickness and vestiture. Adaxial leaf blade cuticles can be thin and papillate, closely reflecting the adaxial epidermis cells (as seen at 30–40\x) or can be thick and smooth. Leaves with thin cuticles dry brown due to brownish granules developing in the epidermis; those with thick cuticles dry gray-green, olive green, or yellowish green without granules in the epidermis cells. Sometimes both types occur in a leaf in either a tight or bold mosaic pattern or the leaf blade may be papillate and brown only along its margins.

Vestiture is mostly sericeous-strigose on leaves, stems, hypanthia, and sepals. The appressed hairs can be slender, short or long (0.2–1.5 mm), appressed, loosely appressed, ascending, or erect. The larger hairs have slender bases that allow them to be strictly appressed, but in some taxa, the base (upon drying) lifts and twists the hair upward, leaving the hairs oriented in many different directions; we refer to this condition as chaotic vestiture. In more densely vestitured plants, very slender, elongate, wavy-curved hairs form an understory beneath the more or less dense sericeous-strigose vestiture.

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

Genera 17, species ca. 240 (9 genera, 25 species in the flora).

A. Cronquist (1981) placed Hydrangeaceae among a group of woody families traditionally allied with Saxifragaceae. Phylogenetic studies consistently place Hydrangeaceae in the Cornales and sister to Loasaceae (A. L. Hempel et al. 1995; D. E. Soltis et al. 1995; L. Hufford et al. 2001; Hufford 2004). Within Hydrangeaceae, the western North American genera Fendlera and Jamesia form a clade (subfam. Jamesioideae L. Hufford) that is sister to the rest of the family (subfam. Hydrangeoideae Burnett) (Hufford et al.; Hufford). Subfamily Hydrangeoideae comprises two tribes: Philadelpheae de Candolle ex Duby and Hydrangeeae de Candolle. North American genera in the former are Carpenteria, Deutzia, Fendlerella, Philadelphus, and Whipplea. A molecular phylogenetic study by Y. De Smet et al. (2015) clarified relationships within Hydrangeeae, found Hydrangea to be polyphyletic, and promoted adoption of a broader concept of Hydrangea that includes the eight other genera in the tribe. The two North American genera in the tribe, Decumaria and Hydrangea, are circumscribed here in their traditional senses.

The Hydrangeaceae are well represented in the paleobotanical record dating back to the Upper Cretaceous but best represented in the Tertiary (L. Hufford 2004). Some genera are sources of popular introduced or native ornamentals, including Carpenteria, Deutzia, Hydrangea, and Philadelphus. Some ornamentals have become established outside of cultivation in the flora area. A few North American Hydrangeaceae have reputed medicinal (D. E. Moerman 1998) or toxicologic (G. E. Burrows and R. J. Tyrl 2001) properties.

Trichomes in most Hydrangeaceae consist of a long, unicellular portion, often borne on a multicellular base. The unicellular portion often bears tubercles on its surface. Sometimes instead of tubercles, it bears long extensions, making the trichome appear branched or dendritic. Such trichomes are here referred to as branched.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Hypanthia and sepal abaxial surfaces glabrous or sparsely to moderately sericeous, hairs not obscuring epidermis.
→ 2
2. Leaf blade adaxial surfaces sparsely sericeous-strigose with appressed or slightly ascending slender hairs; leaf blade margins entire; inflorescences 1(–3)-flowered; capsules 4.4–6 mm; w United States, including se Arizona and sw New Mexico.
var. microphyllus
2. Leaf blade adaxial surfaces sparsely to moderately strigose-sericeous with appressed or loosely appressed thick hairs mixed with erect hairs, or all hairs erect; leaf blade margins usually entire, on larger leaf blades sometimes sparsely serrulate; inflorescences 1–3(–5)-flowered; capsules 5–8 mm; mountains of se Arizona, sw New Mexico.
var. madrensis
1. Hypanthia and sepal abaxial surfaces moderately to densely sericeous-strigose or villous-lanate, often with understory of thinner ± curled hairs usually completely obscuring epidermis except sometimes in fruit.
→ 3
3. Leaf blade abaxial surfaces with hairs usually erect and chaotically oriented, sometimes appressed; mountains of sc New Mexico.
var. argyrocalyx
3. Leaf blade abaxial surfaces with hairs appressed or loosely appressed; w United States, but mostly not sc New Mexico.
→ 4
4. Leaf blade adaxial cuticles forming mosaic of thin, papillate areas and thick, smooth areas, adaxial surfaces drying mosaic of brown and yellowish gray-green, or cuticles uniformly thin, papillate, adaxial surfaces drying dark brown.
var. microphyllus
4. Leaf blade adaxial cuticles thick, smooth, or papillate near margins, adaxial surfaces drying olive green or yellowish gray-green.
→ 5
5. Leaf blade abaxial surfaces with appressed or loosely appressed hairs 0.5–1.2 mm; adaxial surfaces with only appressed or slightly ascending hairs 0.3–0.7 mm; w Texas to sw Arizona.
var. microphyllus
5. Leaf blade abaxial surfaces with appressed or loosely appressed hairs 0.3–0.7 mm, adaxial surfaces with appressed hairs 0.1–0.6 mm and often with shorter erect hairs, 0.1–0.3 mm; California, adjacent w Nevada.
var. pumilus
1. Woody vines.
Decumaria
1. Subshrubs, shrubs, or trees.
→ 2
2. Twigs with stellate and simple trichomes.
Deutzia
2. Twigs glabrous or with simple or, sometimes, branched trichomes, never with stellate trichomes.
→ 3
3. Flowers both sterile and bisexual.
Hydrangea
3. Flowers all bisexual.
→ 4
4. Stamens (11–)13–90 or 150–200.
→ 5
5. Sepals 4; petals 4 (or 8+ in some horticultural forms); ovaries inferior to 1/2 inferior, 4-locular; styles 1 or 4; leaves deciduous; stamens (11–)13–90.
Philadelphus
5. Sepals 5–7; petals 5–7(–8); ovaries nearly superior, 5–7-locular; styles 1; leaves persistent; stamens 150–200.
Carpenteria
4. Stamens 8–12.
→ 6
6. Stems prostrate to decumbent.
Whipplea
6. Stems erect, ascending, or spreading.
→ 7
7. Filament apices 2-lobed, lobes prolonged beyond anthers; seeds (1–)2–4(–6) per locule.
Fendlera
7. Filament apices not 2-lobed; seeds 1 or 10–50 per locule.
→ 8
8. Inflorescences 100–1000-flowered; capsule dehiscence interstylar, creating pore at base of styles.
Hydrangea
8. Inflorescences 1–35-flowered; capsule dehiscence septicidal.
→ 9
9. Leaf blade margins usually crenate to dentate, rarely entire; blades ovate or broadly ovate to obovate, rhombic, or suborbiculate, venation pinnate; seeds 25–50 per locule.
Jamesia
9. Leaf blade margins entire; blades elliptic to lanceolate, oblanceolate, obovate, or linear-oblong, venation acrodromous; seeds 1 per locule.
Fendlerella
Source FNA vol. 12, p. 479. FNA vol. 12, p. 462. Author: Craig C. Freeman.
Parent taxa Hydrangeaceae > Philadelphus
Sibling taxa
P. coronarius, P. hirsutus, P. inodorus, P. lewisii, P. mearnsii, P. pubescens, P. serpyllifolius, P. texensis
Subordinate taxa
P. microphyllus var. argyrocalyx, P. microphyllus var. madrensis, P. microphyllus var. microphyllus, P. microphyllus var. pumilus
Carpenteria, Decumaria, Deutzia, Fendlera, Fendlerella, Hydrangea, Jamesia, Philadelphus, Whipplea
Name authority A. Gray: Mem. Amer. Acad. Arts, n. s. 4: 54. (1849) Dumortier
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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