490 FLORA. 



often pubescent in the axils of the veins beneath, the lobes triangular-ovate, acute, 

 sharply and finely serrate; sterile flower-clusters erect, of numerous small heads, 

 greenish; fertile heads long-peduncled, at length drooping, borne near the base of 

 the sterile; head of fruit about 3-4 cm. in diameter, the fertile seeds few, with nu- 

 merous minute sterile ones. In low woods, Conn, and southern N. Y. to Fla., 

 111., Mo. and Mex. April-May. 



Family 10. PLATANACEAE Lindl. 

 Plane-tree Family. 



Large trees, with alternate petioled palmately lobed and veined leaves, 

 the hollowed petiole bases enclosing the buds for the following season, 

 and small green monoecious flowers in dense globular heads. Recep- 

 tacle 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 ob- 

 long or linear, longitudinally 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. Only the following 

 genus, comprising some 7 species, natives of the north temperate zone. 



i. PLATANUS L. 



Characters of the family. [Name ancient.] Besides the following species, 2 

 others occur in the western U. S. and i or 2 in Mex. 



i. Platanus occidentalis L. BUTTON-WOOD. BUTTON-BALL. PLANE-TREE. 

 (I. F. f. 1881.) A large tree; maximum height about 40 m. ; outer bark freely 

 peeling off in thin plates, uncovering the bright white inner layers. Leaves 

 orbicular, or wider than long, 10-25 cm - wide, cordate or truncate at the base, 

 3-5-lobed, densely floccose- pubescent with whitish branched hairs when young, 

 becoming nearly glabrous when old, the lobes sharply serrate, or rarely entire ; 

 stipules with broad spreading toothed borders, conspicuous on young shoots; fruit- 

 ing heads 2 cm. in diameter, usually solitary, hanging on a long peduncle, persist- 

 ent through the winter. Along streams and in wet woods, Me. to Ont. and Minn., 

 Fla., Kans. and Tex. May. 



Family n. ROSACEAE* B. Juss. 



Rose Family. 



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

 opposite) 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-oo , distinct, or adnate to the calyx. 

 Ovary i-celled or rarely imperfectly 2-celled; style terminal or lateral. 

 Ovules i, 2, or several, anatropous. Fruit mostly follicles or achenes ; 

 endosperm none, or rarely copious. About 65 genera and 1200 species, 

 of wide geographic distribution. 



I. Fruit not enclosed in a hollow receptacle, the so-called calyx. 



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



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



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. 



* Revised by Dr. P. A. RYDBERG. 



