194 



PLATANACEAE. 



[Vol.. II. 

 I8 3 6. 



Family 42. PLATANACEAE Lindl. Nat. Syst. Ed. 2, 187. 



PLANE-TREE FAMILY. 



Large trees, with thin exfoliating bark, alternate petioled patmately lobed 

 and veined leaves, the hollowed petiole bases enclosing the buds for the fol- 

 lowing season, and very small green monoecious flowers in dense globular heads. 

 Receptacle somewhat fleshy. Calyx of 3-8 externally pubescent minute sepals. 

 Corolla of as many thin glabrous petals. Staminate flowers with stamens as many 

 as the sepals and opposite them; filaments short; anthers oblong or linear, longi- 

 tudinally dehiscent. Pistillate flowers with 2-8 distinct pistils; ovary linear, 

 i -celled; style elongated; stigma lateral. Ripened head of fruit composed of 

 very numerous narrowly obpyramidal nutlets which are densely pubescent below 

 with long nearly erect hairs. Seed pendulous; endosperm thin; cotyledons linear. 



The family contains only the following genus, comprising some 7 species, natives of the north 

 temperate zone. 



i. PLATANUS L. Sp. PI. 999. 1753. 

 Characters of the family. [Name ancient.] 

 Besides the following species, 2 others occur in the western United States and i or 2 in Mexico, 



i. Platanus occidentalis L. Button-wood. Button-ball. Plane-tree. 



(Fig. 1881.) 



Platanus occidentalis L,. Sp. PI. 999. 1753. 



A large tree; maximum height about 130 and 

 trunk diameter 14; outer bark freely peeling off 

 in thin plates, uncovering the bright white inner 

 layers. Leaves orbicular, or wider than long, 

 4'-9' wide when mature, cordate or truncate at 

 the base, 3-5-lobed, densely floccose-pubesccnt 

 with whitish branched hairs when young, less so 

 above and becoming nearly glabrous when old, 

 the lobes mostly large, sharply serrate, or rarely 

 entire; petiole mostly shorter than the blade; 

 stipules with broad spreading toothed borders, 

 conspicuous on young shoots; fruiting heads 

 i' in diameter, usually solitary, hanging on a 

 long peduncle, persistent through the winter, 

 the nutlets at length scattered by the wind. 



Along streams and in wet woods, Maine to On- 

 tario and Minnesota, Florida, Kansas and Texas. 

 Wood hard, weak, difficult to split, reddish brown; 

 weight per cubic foot 35 Ibs. The largest tree of 

 east America; often called Sycamore. The outer 

 bark of the lower part of old trunks does not freely 

 exfoliate. May. 



Family 43. ROSACEAE B. Juss. Hort. Trian. 1759. 



ROSE FAMILY. 



Herbs, shrubs, or trees, with alternate (in some exotic genera opposite), 

 simple or compound leaves, and regular perfect or rarely polygamo-dioecious 

 flowers. Stipules commonly present, sometimes large. Calyx free from or adnate 

 to the ovary, 5-lobed (rarely 4-9-lobed), often bracteolate. Disk adnate to the 

 base of the calyx. Petals equal in number to the calyx-lobes, distinct, or none. 

 Stamens usually numerous, distinct; anthers small, 2-celled. Carpels I-QO , dis- 

 tinct, or adnate to the calyx. Ovary i -celled or rarely imperfectly 2-celled; style 

 terminal or lateral. Ovules i, 2, or several, anatropous. Fruit various, mostly 

 follicles or achenes; endosperm none, or rarely copious. 



A family comprising about 65 genera and 1200 species, of wide geographic distribution. 

 Pistils few, seldom more than 5, ripening into 2-4-seeded follicles. 



Follicles dehiscent along both sutures; seeds shining. i. Ofiulaster. 



Follicles dehiscent along one suture; seeds dull. 

 Pistils alternate with the calyx-lobes. 



Flowers perfect; leaves simple; shrubs. 2. Spiraea. 



Flowers dioecious; leaves 2-3-pinnate; tall herbs. 3. Aruncus. 



Pistils opposite the calyx-lobes; petals white, strap-shaped. 4. Porteranthus. 



