=American Cocklebur.= _Xanthium Canadensis_ Mill. Achenes or burs reddish brown, oblong, circular in section, two-beaked, about 20 mm. long, covered with stout hooked prickles. Each bur encloses two seeds. Native of this country. [Illustration: Fig. 215.] =Spiny Clotbur.= _Xanthium spinosum_ L. Bur oblong, light brown, very slightly flattened, 10-13 mm. long, the beaks weak and small, small hooked prickles 3-4 mm. long, each bur contains two seeds. Introduced from Europe. =Broad Cocklebur.= _Xanthium strumarium_ L. Bur dark brown, oval, circular in sections 12-22 mm. long, beaks stout, nearly straight, spines about 5 mm. long, surface of burs and base of spines clothed with minute hooked prickles. Naturalized from Europe. INDEX. Page Abutilon, 145 Acalypha, 143 AC-CUM´BENT, leaning or lying upon, applied to cotyledons when the caulicle (radicle) is folded against their contiguous edges, shown as [Symbol: 0== rotated 90 deg. clockwise]. A-CHENE´, achenium, a small, dry, one-seeded, indehiscent fruit, likely to be mistaken for a seed. Achillea, 160 Acnida, 126 A-CU´MIN-ATE, ending in a prolonged tapering point. Agrimonia, 138 Agrimony, tall hairy, 138 Agrostemma, 128 Agropyron, 110 Aizoaceae, 128 Alfalfa, 140 Allium, 119 Alfilaria, 142 Alsike clover, 141 Alsine, 131 Alyssum, 132 Alyssum, hoary, 133 Amaranth, 126, 127 Amaranth family, 126 Amaranthaceae, 126 Amaranthus, 127 Ambrosia, 160, 161 American jute, 145 Anacardiaceae, 145 A-NAT´RO-POUS, a name applied to an ovule or seed which grows so that the funiculus coheres to the whole length forming a raphe along the edge bringing the hilum near the micropyle while the chalaza is at the other extremity. Annual fleabane, 165 Anthemis, 161 Apetalous pepper-grass, 135 A´PEX, the tip or growing point of an organ. Arctium, 162 Arenaria, 129 Artemisia, 162 Artichoke, 167 Asclepiadaceae, 149 Asclepias, 149 Atriplex, 124 Avena, 110 AWN, a bristle-shaped appendage. Ax seed, 139 Ax wort, 139 Ball mustard, 137 Barbarea, 133 BARBED, furnished with rigid points or short bristles, usually reflexed like the barb of a fish-hook. Barnyard grass, 114 Beaked nightshade, 156 Beaver poison, 148 Beggar-ticks, 163 Bermuda grass, 113 Berteroa, 133 Bidens, 162, 163 Biennial wormwood, 162 Bindweed, 150 Bird's-foot trefoil, 139 Bitter buttercup, 131 Bitter dock, 122 Black-eyed susan, 169 Black medick, 139 Black mustard, 134 Black nightshade, 156 Black swallow-wort, 149 Bladder campion, 130 Bladder Ketmia, 146 Bloom-fell, 139 Bluefield madder, 159 Blue grass, 116 Blue grass, Canadian, 116 Blue grass, Kentucky, 116 Blue Vervain, 153 Borage family, 152 Boraginaceae, 152 Bouncing Bet, 129