KEY TO THE FAMILIES BASED MAINLY UPON FLOWERS. 



a Flowers unisexual, with ovules naked on the face of a scale : leaves parallel-veined 

 (GumnospcrnHe), monoecious; ovules 2 or more with esich scale: stamens numerous; fruit a 

 cone with imbricated scales or so modified as to resemble a berry. 



Coniferse ( j). 418). 

 a' Flowers with ovules inclosed in a cavity — ovary — (Augio.sixrma'} and the parts of the 

 flower in 4s or 5s; cotyledons 2 {Dicotyledons) ; flowers 

 b Without a corolla (Apctalce), 

 c Fnisexual and 



d Calyx absent or irregular if present ; flowers appearing 

 e After the leaves, the staminate 



f From axillary buds on growth of the previous season, in drooping aments ; 

 pistillate solitary or in few-flowered spikes terminating new shoots on the same tree; fruit a 



nut; leaves compound, deciduous Juglandacese (p. 423). 



f- From the axils of evergreen simple leaves, in erect aments ; fruit a wax-coated 



berry Myricacese (p. 424) . 



f^ Mostly from the axils of bud-scales at the base of new shoots and in 

 g Drooping 



h Long-peduncled heads; the pistillate solitary or in pairs terminating shoots 



on the same tree Fagus, in Fagacese (p. 429), 



h- Slender drooping aments ; pistillate flowers from axils of leaves on the 



same shoots Quercus, in Fagaceae ( p. 430) . 



g- Erect axillary aments ; the pistillate at the bases of the same aments, 

 Castanea, in Fagacese (p, 430), 

 t' In heads arranged in terminal racemes. 



Liiquidambar, in Hamamelidacese (p. 437). 

 e' Before or with the leaves 



f P"'rom axillary buds which are 



g Covered with one or more bud-scales 



h Both staminate and pistillate flowers in aments and on different trees, 



Salicacese (p. 42.5). 

 h- Staminate only in aments; the pistillate in slender terminal spikes on 



same tree Carpinus, in Betulacese. 



h^ In panicles, dioecious, without petals; leaves compound; fruit a samara. 

 Fraxinus, in Oleacese. 

 g= Naked — not covered with true bud-scales ; ovary superior ; fruit an elongated 



compressed drupe Ijeitneriacese (p. 425) . 



f- Tei-minating shoots of the previous season and 



g The staminate (only) remaining naked during the previous winter; the 

 pistillate in spikes from lateral buds ; staminate aments 



h Simple; fruit a strobile., Betula, in Betulaceae (p. 428). 

 h- Compound, 2-5 (usually 3) united at base; fruit resembling a hop. 

 Ostrya, in Betulaceae (p. 428). 

 g- Both staminate and pistillate remaining naked during previous winter, on 



same branchlets AInus, in Betulaceae ( p. 425)) . 



d- Calyx present and regular ; flowers appearing after the leaves ; dioecious ; calyx 

 becoming enlarged and succulent in the compound fruit. 



Moraceae (p. 433). 

 e= Perfect ; calyx present, regular ; ovary superior, 1-celled and usually 1-seeded ; flowers 

 in fascicles or racemes before or with the leaves ; fruit a 

 d Samara, winged 



e Nearly or quite all around Ulmus, in Ulmaceae (p. 432). 



e- Obliquely from one end and arranged in pairs. 



Acer, in Aceraceae (p. 446). 



d= Drupe Lauraceae ( p. 435 ) . 



b' With a corolla and that consisting of 

 c Separate petals (Poli/pctalw) 

 d Ovary superior 



e Flowers perfect and 

 f Regular 



g Calyx consisting of three sepals ; stamens numerous ; pistils 

 h Numerou.s, from an elongated rpcei)tacle ; ovary 2-()Vuled. 



Magnoliacese {]>. A'.W ) . 

 hr Few, from a globose receptacle : ovary niany-ovulrd. 



Asiniina, in Anonacese (p. 435), 

 [ix] 



