CLASS DIDYNAMIA. 
171 
lyx or perianth ; 2d, with a perianth. In the first section we find 
several interesting native plants. The Clematis or Vir^rin's bower 
is a beautifiil climbing plant, which supports itself by winding its 
petiole or leaf-bearing "stems around other plants ; the flowers are 
white and clustered in corymbs ; the seed has a long silk-like 'ringo, 
which gives it a fine appearance after the blossoms have faded. 
This plant contains many species, and is cultivated both in this 
country and in Europe. At fig. 136, a, is a flower of the Clematis; 
6, represents its receptacle with numerous styles proceeding from it, 
and the petal and stamens separated, showing them to be inserted 
upon the receptacle. 
The Hellebore {Helleborus) is an exotic much spoken of by clas- 
sical writers. Hippocrates, one of the most ancient physicians, 
remarked upon its qualities; it grew about Mount Olympus, and was 
early known as a very poisonous plant. 
The Magnolia and Tulip-tree are among the most splendid trees 
of North America; they are said also to be common to China. 
The region of the Magnoha grandiflora extends from South Caro- 
Una to the isthmus of Darien. In some cases these trees rise to the 
height of 90 feet before sending oflT any considerable branches ; the 
spreading top is then clothed with deep green, oblong-oval leaves, 
like a laurel; these are, at most seasons, enlivened by large and 
fragrant white flowers. 
The class Polyandria, though not important for its fruits, con- 
tains some valuable medicinal plants, besides those which we have 
noticed. 
LECTURE XXXII. 
CLASS DID-VNAMIA AND TETRADYNAMIA. 
The two classes which are to afford subjects for our present ob- 
servations, are founded upon the number and relative length of the 
stamens. In distinguishing their orders, the number of styles is not 
regarded, but new circumstances of distinction are introduced, viz. 
the seeds being enclosed in a pericarp, or 
destitute of this covering, and the compar- 
ative length of pods. 
CLASS XIIL DIDYNAMIA. 
This class has flowers with 4 stamens, two of 
which are longer than the other two; the 
stamens stand in pairs ; the outer pair be- 
ing longer, the inner pair shorter and con- 
verging. 
The class contains two orders, Gymnos- 
permia, (seeds naked or without a pericarp,) 
and Angiospermia, (seeds enclosed in a per 
ricarp.) 
Tlie labiate flowers are found in this class ; these are monopeta- 
lous, and irregular in their outline. The term labiate is derived 
from the Latin labia, signifying lips ; the flowers being divided at 
the top into two parts, resembling the lips of an animal. This tribe 
Clematis — Hellebore — Magnolia— What classes are now considered']— How ar6 
their orders diat'nguislied 7 — L nbiate flowers. 
