KEY TO THE FAMILIES BASED MAINLY UPON FLOWERS. 



a Flowers unisexual, with ovules uaked. on the face of a scale ; leaves parallel-veined 

 (Gymnosperm(r) , monoecious; 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 cavity — ovary — (Aitc/iospermo') and the parts of the 

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

 b Without a corolla (Apetalw), 

 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 Juglandaceae (p. 423). 



t' From the axils of evergreen simple leaves, in erect aments ; fruit a wax-coated 



berry Myricaceae (p. 424) . 



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

 g Drooping 



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



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



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



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



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

 Castanea, in Fagacese (p. 430). 

 f* In heads arranged in terminal racemes. 



Liquidambar, in Hamamelidacese ( 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. 



Salicacese (p. 425). 

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



same tree Carpinus, in Betulacese. 



b^ 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 Leitneriacese (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). 

 b* Compound, 2-5 (usually 3) united at base: fruit resembling a hop. 

 Ostrya, in Betulacese (p. 428). 

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



same branchlets Alnus, in Betulacese (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 Ulmacese (p. 432). 



e- Obliquely from one end and arranged in pairs. 



Acer, in Aceracese (p. 446). 



d- Drupe Lauracese (p. 435) . 



b' With a corolla and that consisting of 

 c Separate petals .( Polypetalw) 

 d Ovary superior 



e Flowers perfect and 

 f Regular 



g Calyx consisting of three sepals ; stamens numerous : pistils 

 b Numerous, from an elongated receptacle: ovary 2-ovuled. 



Magnoliacese ( p. 434 ) . 

 b' Few, from a globose receptacle : ovary many-ovuled. 



Asimina, in Anonaceae I p. 435). 

 [ix] 



