KEY TO XATUEAL OKDEES. 



23 



B. FlOWEES, one or both sorts. IX A31EXTS OR CATKIX-LIEE HEADS. 



Twining dioecious herbs ; fertile flowers only in p^gj 

 short amentg. Humulus in Urticace^, 2'Jl 



Shmbbv plants, parasitic on trees. Fruit a berry, Loraxthace^, 286 

 Trees or shrubs. 



Sterile flowers only in aments. Flowers 

 moncEcious. 



Leaves pinnate. Orarr and fruit with- 

 out an involucre. Juglaxdace^, 303 

 Leaves simple. Xuts one or more in a 



cup or involucre. Cupulifer^, 307 



Tlowers of both kinds in aments or close 

 heads. 



Leaves palmatelv-veined or lobed. 



Calvx 4-cleft, in the fertile flowers 



becoming berrv-like. Morus in TJrticace^, 291 

 Calyx none: flowers in round heads. PLATAXACEiE, 301 

 Leaves pinnately-veined. 



Flowers dioecious, 1 on each scale. 



Pod many-seeded. Salicace^, 328 



Flowers monoecious, the fertile ones 



2 or more under each scale. Betulace^, ^24 



Flowers only 1 under each fertile 

 scale. 



Fruit 1 -seeded. Mteicace^, 323 



Sub-class 2. Gyjixosperms. Pisiil represented by an open scale or leaf, 

 or sometimes entirely wanting ; the ovules and seeds naked. 

 Flowers monoecious or dioecious. Stems 



branched. Leaves simple. CoxiFEKa:, 333 



