30 ANALYTICAL KEY. 



2. Both sterile and fertile flowers in catkins or catkin-like heads. 

 Ovary and pod 2-celled, many-seeded. Liquidambar, in Hamamelace^j, 173 

 Ovary and pod i -celled, many-seeded; seeds furnished with 



a downy tuft at one end. Salicace^j, 461 



Ovary 1 -2-celled, only one ovule: in each cell : fruit 1-seeded. 

 Parasitic on trees : fruit a berry. .... Loranthace^e, 426 



Trees or shrubs, not parasitic. 



Calyx regular, in the fertile flower succulent in fruit. Urticaceje, 440 

 Calyx none, or rudimentary and scale-like. 



Style and stigma one, simple : the flowers in heads. Platanace^e, 446 

 Styles or long stigmas 2. 

 Fertile flowers 2 or 3 under each scale of the catkin. Betulace^e, 458 

 Fertile flowers single under each scale : nutlets 



naked, waxy-coated or drupe-like. . . . Myricace^e, 457 

 Fertile flowers in pairs at each scale, each in a mem- 

 branous sac or with leafy bractlets. Carpineas, in Cupulifer^e, 449 



Subclass II. GYMNO SPERMS. Pistil an open scale or altered 

 leaf, bearing naked ovules on its margin or its upper surface, or in Taxus 

 entirely wanting. Flowers monoecious or dioecious. 



Represented in the Northern United States only by the order Conifers, 468 



Class II. MONOCOTYLEDONOUS or ENDOGENOUS PLANTS. 



Stems with the wood collected into separate bundles or threads, which 

 are irregularly dispersed throughout the whole diameter, leaving no dis- 

 tinct pith in the centre ; not forming annual layers. (A transverse 

 slice of the stem therefore exhibits the woody threads as dots scattered 

 throughout the cellular tissue.) Leaves mostly parallel-veined (occasion- 

 ally more or less reticulated). Embryo with a single cotyledon, and the 

 first leaves in germination alternate. Parts of the flower generally in 

 threes, never in fives. 



A. Spadiceous Division. Flowers aggregated on a spadix or fleshy axis, or 

 sometimes scattered, destitute of calyx and corolla {excepting some Araceae and 

 Naiadacese, where, however, they are on a spadix), and also without glumes 

 (husky scales). Leaves sometimes with netted veins. 



Little floating aquatics, with no distinction of stem and foliage. Lemnaceye, 478 



Immersed aquatics, branching and leafy Naidaceve, 482 



Heed-like or Flag-like marsh herbs, with linear and sessile 

 nerved leaves : flowers in spikes or heads. 

 Flowers monoecious, and quite destitute of floral envelopes. Typhace/E, 480 

 Flowers perfect, on a lateral spadix : sepals 6. Acorus, ) 



Terrestrial or marsh plants : leaves mostly with a distinct >■ AraceyE, 475 



netted-veined blade, petioled. ) 



