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.e. 



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



sected. 



(255) Callitriche — leaves opposite, entire. 



55. Urticaceous Plants. Urticace.s.. 



(256) XJrtica — 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. Polyg^onaceous Plants. Polygonace.e. 



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



coming enlarged. 

 (2G0) Oxyria — perianth four-parted, the two inner segments en- 

 larged. 



