NATUKAL ORDERS. 



257 



styles ; c, vertical section of the base of the pistil and receptacle, magnified ; d, a 

 transverse section of the seed, sliowing the leafy convolute cotyledons. 



430. LiNACEiE, the Flax Tribe. — Herbs with entire, and sessile 

 leaves^ usually alternate, and exstipulate. Sepals 3-5, persistent, 

 with an imbricated aestivation. Petals as many as the sepals, 

 with a twisted restivation. Stamens equal in number to the 

 petals, with which they alternate usually with intermediate 

 teeth, or abortive stamens, all united at the* base into a hypo- 

 gynous annular disk. Ovary with as many styles and cells as 

 sepals ; stigmas capitate ; ovules pendulous. Fruit a many- 

 celled capsule, each cell more or less completely divided by a 

 false dissepiment arising from the dorsal suture. Seeds single 

 in each spurious cell ; embryo straight, surrounded by a thin 

 albumen ; cotyledons flat, fleshy, and oily. 



a. Properties : these plants yield mucilage and fiber which are valuable. 

 Genus. — Linum. 



431. OxALiDACE^, the Wood-Sorrel Trihe. — Low herbs with 

 alternate, compound leaves., generally without stipules. Sepals 5, 

 equal, persistent, imbricate in aes- 

 tivation. Petals 5, unguiculate, 

 with a twisted aestivation. Sta- 

 mens 10, monadelphous, in 2 rows, 

 those opposite the petals being 

 longer than those in the outer 

 row. Carpels 5, united into a 

 compound ovary ; styles distinct. 

 Fruit a membranaceous, 5-lobed, 

 5-celled capsule. Seeds few, at- 

 tached to a central placenta ; em- 

 bryo large and straight, in thin 

 albumen. 



a. Properties : the herbage is sour, and con- 

 tains oxalic acid. Some plants of this order 

 yield esculent roots. 



Genus. — Oxalis. 



Fig. 182, a, Oxalis violacea, -with the bulb 

 as in summer, producing numerous subter- 

 ranean branches, and a thickened root below ; 

 b, tlie pistil, with the ring of stamens laid open 

 .,:«„,!. ^ j^jj ovule, more magnified. 



nified 



vertical section of a pistil, mag 



^ 432.^ Zygophyllace^. — Herbs, shrubs., or trees. Leaves oppo- 

 site, stipuled, usually compound. Calyx 4 or 5 parted, convo- 

 lute in aestivation. ^Petals alternate with the segments of the 

 calyx, imbricated in aestivation. Ovary simple, 4 or 5 celled. 

 Fmit capsular, with 4 or 5 angles or wings. Seeds few, with 

 whitish albumen ; embryo green ; cotyledons foliaceous. 



Genus. — Tribulus. 



