46 NORTH AMERICAN FLORA [VoLuME 29 
equal, entire. Stamens 5-10, not declined; filaments very slender; anthers obovoid or globular. 
Ovary 5-celled, depressed; style rather slender, slightly curved, dilated at the apex; stigma 
4-lobed. Capsule short and stout, surrounded by the calyx. 
Type species, Rhododendron albifilorum Hook. 
1. Azaleastrum albiflorum (Hook.) Rydb. Mem. N. Y. Bot. 
Gard. 1: 297. 1900. 
Rhododendron albiforum Hook. F1. Bor. Am. 2:43. 1834. 
Azalea albiflora Kuntze, Rev. Gen. 387. 1891. 
?Cladothamnus campanulatus Greene, Erythea 3:65. 1895. 
Shrub 2 m. tall or less, with usually pale, coarsely and finely pubescent branchlets; leaf- 
blades oblong, elliptic, or oval, or somewhat broadened upward, 2-7 em. long, acute or abruptly 
gland-tipped, bright-green and often somewhat shining above, paler and often slightly pu- 
bescent beneath, undulate or repand-crenate, the short petioles pubescent; pedicels copiously 
pubescent; calyx-lobes oblong varying to ovate or obovate, mostly 9-12 mm. long, finely 
pubescent; corolla usually white, 2 cm. long or less, the lobes very broad, about as long as the 
tube; filaments very pubescent at least from the middle to the base; capsules ovoid, 7-10 mm. 
long, pwhbescent. 
Type Locality: Alpine woods of the Rocky Mountains. 
no Northern Rocky Mountains, as far south as Montana, to British Columbia and 
ILnLustRatTions: Hook. Fl. Bor. Am. pl. 133; Bot. Mag. pl. 3670; Henshaw, Mountain Fl. Am. 
pl. 97; Brown & Schiffer, Alp. Pl. Can. pi. 60. 
DouBTFUL SPECIES 
AZALEASTRUM WARRENII A. Nelson, Bot. Gaz. 54: 67 (1913), described from specimens collected 
on Mt, Zirkel, Jackson County, Colorado, may be distinct from Azaleasirum albiflorum. We have 
not seen specimens, and Professor Nelson does not compare the two species in his description. 
11. RHODODENDRON L. Sp. Pl. 392. 1753. 
Shrubs or small trees, with glabrous, pubescent, or glandular-waxy foliage and deciduous 
bud-scales. Leaves alternate, scattered or sometimes approximate at the ends of the branches; 
blades broad, thick, often leathery, entire, petioled. Flowers in usually dense clusters which 
appear before or after the leafy shoots of the season. Calyx usually saucer-shaped, small; 
lobes 5, short and inconspicuous, persistent. Corolla white or colored, campanulate, or rotate- 
campanulate, deeply lobed; lobes 5, unequal, broad, flat or crisped. Stamens mostly 10 or 
rarely 5, shorter than the corolla or not much longer; filaments slender, declined; anthers short, 
mostly oval or obovoid. Ovary 5-celled, shallowly lobed, depressed or slightly elongate; 
style curved, elongate, enlarged at the apex; stigma sometimes obscurely lobed. Capsule 
narrowly ovoid to oblong, thick-walled. 
Type species, Rhododendron ferrugineum L,. 
Leaf-blades not glandular-dotted or scaly. 
Pedicels glandular or pubescent, at least in anthesis; plants of the Atlantic 
States. 
Calyx-lobes longer than wide; corolla mainly white or pink; pedicels 
viscid. 1. R. maximum. 
Calyx-lobes wider than long; corolla rose-purple or lilac-purple; pedicels 
not viscid. 2. R. catawbiense. 
Pedicels glabrous; plants of the Pacific States. 
Corolla rose-purple, 3 cm. long or more. 3. R. californicum. 
Corolla white, less than 3 cm. long. 4. R. macrophyllum 
Leaf-blades glandular-dotted or scaly. 
Erect shrubs; corolla funnelform or campanulate-funnelform. 
Flower-clusters appearing after the leafy shoots of the season; leaf- 
blades acute or acuminate. 
Corolla 1.5-2 em. long; calyx-lobes of a deltoid type. 5. R. cavolinianum. 
Corolla 2.5-3 em. long; calyx-lobes of an ovate type. 6. R: minus. 
Flower-clusters appearing before the leafy shoots of the season; leaf- 
blades obtuse or retuse. 7. R. Chapmanii. 
Depressed shrubs; corolla rotate-campanulate. 8. R. lepponicum. 
