NATUKAL OKDERS. 



259 



437. AcEKACEuE, the, Maple Tribe. — Trees with opposite, sim- 



?le, rarely pinnate leaves, 

 ^lowers often polyga- 

 mous. Calyx divided 

 into 5, occasionally 4-9 

 parts. Petals as many 

 as the lobes of the calyx, 

 inserted romid a hypo- 

 gynous disk, or wanting. 

 Ovary free, 2-lobed ; style 

 1 ; stigmas 2 ; ovules pen- 

 dulous, in pairs. Fruity 

 a samara composed of 2- 

 winged carpels, each 1- 

 celled, 1 or 2 seeded. 

 Seeds solitary, destitute 

 of albumen. Eiiibnjo 

 coiled. 



a. Properties : useful timber- 

 trees ; the sap of A. saccharinum 

 yields sugar. 



Genera. — Acer, Negundo. 



Fig. 183, a, Acer saccharinum (sugar -maple) ; branch of a staminate plant m 

 flower ; h, a staminate flower, enlarged ; c, a pistillate flower with the calyx laid 

 open, showing the short stamens, disk, etc. ; d, the pistil of the same, the other 

 organs removed ; e, the fruit, one carpel cut open to show the seed. 



438. Sapindaceje, tlie Soap-tree Tribe. — Trees or twining 

 shrubs. Leaves alternate, compound, often marked with lines 

 or pellucid dots. Flowers small, irregular. Sepals 4 or 5, dis- 

 tinct, or cohering at the base. Petals 4-5, occasionally want- 

 ing, alternate with the sepals. Stamens 8-10. Ovary 2 or 3 

 celled ; ovules ascending or suspended. Fruit a capsule, or 

 samara, or fleshy and indehiscent. Seeds usually with an aril, 

 exalbuminous ; embryo coiled. In this order are included Hip- 

 POCASTAN^E or Horse-chestnuts. 



a. Properties : sometimes used as a substitute for soap ; astringent and bitter. 

 Genera. — Cardiospermum, Sapindus, Dodonea, uEsculus, 



439. StaphylacEuE, the Bladder-omt Tribe. — Shrubs with op- 

 posite, pinnate leaves. Sepals 5, united at the base, colored. 

 Petals 5, alternate, aestivation imbricate. Stamens 5, alternate 

 with the petals. Disli, large, nrceolate. Ovary ^1-Z-q.^%^\ 

 ovules usually ascending. Fruit membraneous or fleshy. Seeds 

 with a bony testa, without albumen ; embryo straight ; cotyle- 

 dons thick. 



a. Properties : sub-acrid, or bitter and astringent. 

 Genus. — Staphylea. 



440. Celastrace^, the Spindle-tree Tribe. — Small trees or 



