GENERA OR FAMILIES. 173 



** Stem continuous ; leaves semicylindrical. 



(249) Suseda leaves succulent, not prickly ; perianth segments 



remaining unaltered. 



(250) Salsola leaves prickly; perianth segments acquiring a 



dorsal appendage or wing. 



*** Stem continuous ; leaves flat. 



(251) Beta perianth segments succulent, becoming enlarged, 



with the lower half of the ovary adherent to them. 



(252) Chenopodium perianth segments herbaceous, scarcely 



enlarged, the ovary free. 



(253) Atriplex polygamous or monoecious ; perianth of female 



flowers, consisting, when in fruit, of two much enlarged 

 segments. 



54. Ceratophyllaceous Plants. CERATOPHYLLACE^;. 



(254) Ceratophyllum leaves whorled, 2-3 times furcately dis- 



sected. 



(255) Callitriche leaves opposite, entire. 



55. Urticaceous Plants. URTICACE^. 



(256) Urtica perianth of female flowers two-sepaled ; stamens 



four. 



(257) Parietaria perianth of female flowers four-cleft ; stamens 



four. 



(258) Humulus perianth of female flowers a mere scale ; sta- 



mens five. 



56. Polygonaceous Plants. POLYGON AC EM. 



(259) Rumex perianth six-parted, the three inner segments be- 



coming enlarged. 



(260) Oxyria perianth four-parted, the two inner segments en- 



larged. 



