32 KEY TO PLANTS. 
Stigma 1, lateral. Ovule laterally af- 
fixed. Shrubs. North America. 
Levtnerieae. 
(4) All flowers furnished with a perianth. 
Perianth with two or more valvate seg- 
ments, or nearly entire and plaited in 
bud.* Style 1, undivided,or 0. Stigma 
1 34. 
34 (a) Stamens hypogynous, free from the 
perianth, rarely cohering a little with 
it ; in the latter case herbs with opposite 
leaves. 30. 
(6) Stamens inserted on the perianth or on 
a perigynous disc. Shrubs or trees, 
rarely undershrubs with alternate leaves. 
38. 
35 (a) Submerged aquatic plants. Leaves 
whorled, dichotomously divided.  Peri- 
anth-segments 6-12. Ovule pendulous. 
Seed exalbuminous. Herbs. Stamens 
10-20. Ceratophylleae. 
(6) Terrestrial plants. Leaves alternate or 
* Compare some Oompositae, the female flowers of 
which are destitute of a perianth, but enclosed by a gamo- 
phyllous involucre. They have a 2-partite style, the 
stamens inserted on the perianth, and usually herbaceous 
stems. 
