genus archaeornis genus archeopteryx genus archidiskidon genus archilochus genus architeuthis genus archosargus genus arctictis genus arctium genus arctocebus genus arctocephalus genus arctonyx genus arctostaphylos genus arctotis genus ardea genus ardisia genus areca genus arenaria genus arenga genus arethusa genus argemone genus argentina genus argentinosaurus genus argiope genus argonauta genus argusianus genus argynnis genus argyranthemum genus argyreia genus argyrotaenia genus argyroxiphium genus arilus genus ariocarpus genus ariomma genus arisaema genus arisarum genus aristolochia genus aristotelia genus arius genus arizona genus armadillidium genus armeria genus armillaria genus armillariella genus armoracia genus arnica genus arnoseris genus arrhenatherum genus artamus genus artemia genus artemisia genus arthropteris genus artocarpus genus arum genus arundinaria genus arundo genus arvicola genus asarum genus ascaphus genus ascaridia genus ascaris genus asclepias genus ascophyllum genus asimina genus asio genus aspalathus genus asparagus genus aspergillus genus asperula genus asphodeline genus asphodelus genus aspidelaps genus aspidiotus genus aspidistra genus aspidophoroides genus aspis genus asplenium genus astacus genus aster genus astilbe genus astragalus genus astrantia genus astreus genus astroloma genus astronium genus astrophyton genus astropogon genus ateles genus athene genus atherinopsis genus atherurus genus athrotaxis genus athyrium genus atrichornis genus atriplex genus atropa genus attalea genus atticus genus aucuba genus aulacorhyncus genus aulostomus genus aureolaria genus auricularia genus auriparus genus australopithecus genus austrocedrus genus austrotaxus genus automeris genus avahi genus avena genus averrhoa genus avicennia genus ayapana genus aythya genus azadirachta genus azolla genus babesia genus babyrousa genus baccharis genus bacillus genus bacteroides genus baiomys genus bairdiella genus balaena genus balaeniceps genus balaenoptera genus balanus genus balistes genus ballota genus balsamorhiza genus bambusa genus bankia genus banksia genus baphia genus baptisia genus barbarea genus barosaurus genus bartle-frere genus bartramia genus basiliscus genus bassariscus genus bassia genus bathyergus genus batis genus batrachoseps genus bauhinia genus beaumontia genus begonia genus belamcanda genus bellis genus bemisia genus bennettitis genus benzoin genus berberis genus bergenia genus beroe genus berteroa genus bertholletia genus bessera genus besseya genus beta genus bettongia genus betula genus bibos genus bidens genus bignonia genus biscutella genus bison genus bitis genus blaberus genus blandfordia genus blarina genus blastocladia genus blastomyces genus blatta genus blattella genus blechnum genus blennius genus blephilia genus bletia genus bletilla genus blighia genus blissus genus bloomeria genus bocconia genus boehmeria genus bolbitis genus boletellus genus boletus genus boltonia genus bomarea genus bombax genus bombina genus bombus genus bombycilla genus bombyx genus bonasa genus borago genus borassus genus borrelia genus bos