253 PRACTICAL BOTANY. 



pearance of one of the cells, an achenium. Leaves heart- 

 ovate, sen-ate, often-lobed. Morus (870). 



{Mulberry.) 



796. Ovary 1-celled, 1-seeded. Fruit a nutlet. , BQth 



sorts of flowers in spherical heads, the fertile heads long-pe- 



duncled, pendulous. Leaves angularly sinuate-lobed or 



toothed, large ; lobes sharp-pointed. 



Flatanus ocddentalis, L. 

 {Buttonwood. Sycamore.) 

 Ovary 2-celled, consisting of 2 pistils united below ; 

 the cells many-seeded. Fruit a 2-celled, 2-beaked pod. Fer- 

 tile flowers in spherical, long-peduncled, drooping heads (in 

 fruit a globose strobile with the pods immersed into its 

 scales). Sterile flowers in a conical, erect ament. Leaves 

 deeply 5- to 7-lobed ; lobes long, acuminate, serrate ; veins 

 villous at their bases. Liquidambar stryaciflua, L. 



{Sweet-gum Tree.) 

 yOy. (775.) Staminate and pistillate flowers, each sort in 

 a common (calyx-like) involucre of distinct, or united scales, 

 composing what is called a head ; both kinds of heads on 

 the same plant — the pistillate heads only 1- or 2-flowered, the 

 staminate (open-cup-shaped involucres) with several flowers, 



intermixed with chaff 798 



No common, calyx-like involucre to several flowers. 



799 



798, Fertile heads, each in a 1-leaved, entire, or 5-tooth- 

 ed, 1 -flowered involucre (the flower naked — that is, a 2-styled 

 ovary), 1-3 together in the axils. Sterile heads (about as 

 large as a pea) composed of 7-12 scales, united into a cup, 

 5- to 20-flowered ; flowers funnel-form ; heads in cylindric 

 spikes or panicled racemes. Herbs, 1-12 feet high. 



Ambrosia (935). 

 Fertile heads, each a prickly, 2-leaved, 2-flo-wered, 

 2-beaked, coriaceous, ovoid or oblong involucre, forming a 

 bur ; its flowers consisting of a pistil with a slender, filiform 

 corolla. Sterile heads : involucres of distinct scales, contain- 

 ing several staminate, tubular flowers. Racemes of flowers 

 compact, in the axils, the sterile flowers above. Herbs some- 

 times spiny, with the spines 3-parted. Xauthium (932). 



799. Flowers, at least the sterile, with both calyx and 

 corolla 800 



