KEY TO THE FAMILIES BASED MAINLY UPON FLOWERS. 



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

 (Gumnospcrma'}, niono?cious ; ovules 2 or more with each scale; stamens numerous; fruit a 

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



Coniferse (p. 418). 

 a' Flowers with ovules inclosed in a cavit,y — ovary — (Angiosiyermce) and the parts of the 

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

 b Without a corolla {Ajjetalw), 

 c Unisexual 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 Jnglandacese (p. 423). 



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



berry Myrieaeese (p. 424) . 



t' Mostly from the axils of bud-scales at the base of new shoots and ia 

 g Drooping 



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



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



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



same shoots Quercus, in Fagaceae (p. 4.30) . 



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



Castanea, in Fagaceae (p. 430). 

 t' In heads arranged in terminal racemes. 



Iiiquidambar, in Hamamelidaceae (p. 487) . 

 e' Before or with the leaves 



f From axillary buds which are 



g Covered with one or more bud-scales 



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



Salicaceae (p. 425). 

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



same tree Carpinus, in Betulacese. 



K' In panicles, dicecious, without petals; leaves compound; fruit a samara. 



Fraxinus, in Oleaceae. 

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



compressed drupe Leitneriaceae (p. 425) . 



f= Terminating 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 Betulacese (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 Alnus, in Betulaceae (p. 429). 



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

 becoming enlarged and succulent in the compound fruit. 



Moracese (p. 433). 

 c= 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 (Polypetalw) 

 d Ovary superior 



e Flofl-ers perfect and 

 f Regular 



g Calyx consisting of three sepals ; stamens numerous ; pistils 

 h Numerous, from an elongated receptacle ; ovary 2-ovuled. 



Magnoliaceae (p. 434). 

 h^ Few, from a globose receptacle ; ovary many-ovuled. 



Asimina, in Anonacese (p. 435). 



[ix] 



