CLASS TETRANDEIA. 
13T 
natural family; the genera which compose it appearing little 
united by natural relations. 
1Y8. Order Monogynia^ one pistil. — 
HousTONiA Gcerulea is known by differ- 
ent common names ; as Innocence^ Ye- 
nus^s Pride^ and Blue Iloustonia. It is 
a very delicate little flower, appearing 
early in the spring, in grassy fields and 
meadows ; the color varies from sky-blue 
(which gives its specific name, ccerulea) 
to pure white. It has a small calyx 
with four sepals, and a monopetalous co- 
rolla of four deep divisions, which gives 
it the appearance of a cruciform plant. 
The common Plantain {Plantago^ Fig. 133, a) is found here. 
The flowers grow on a spike ; they are very small, but each one 
has a calyx and corolla ; these are four-parted ; the filaments 
are long ; the pericarp ovate, with two cells. 
179. Aggregate Flowers. — We find in this class what Linnaeus 
called the aggregate flowers. This term is used when many 
flowers are situated on the same receptacle ; they have a gen- 
eral resemblance to the compound flowers in the class Syn- 
genesia, but differ from them in having but four stamens, with 
anthers separate, while the Syngenesious plants have five 
united anthers. The aggregate flowers are not often yellow 
like many of the compound flowers, but are usually either 
blue, white, red, or purple. The button-bush {Cephalanthus) 
is a shrub of about flve feet in hight. The inflorescence is white, 
appearing in large heads of a globular form, each consisting of 
many perfect little florets. Only one species of this genus, the 
OGGi 'dentalis^^ is known, and this is entirely confined to North 
America. The Gornus (from cornu.^ a horn, so called on ac- 
count of the hardness of the wood) is a genus composed mostly 
of shrub-like plants with flowers growing in flat clusters, or 
cymes. The florida^ a species of cornus called dog- wood, is a 
beautiful ornament of our woods. It is from fifteen to thirty 
feet in hight. Its real corollas are very small, but the head 
or cyme is surrounded by an involucrmn of four large ob- 
ovate leaves, usually white, but sometimes of a pale rose- 
color ; hence its specific name florida.^ or florid. The large 
leaves of the involucrum might at flrst sight be regarded as 
petals. At Fig. 133, J, is a representation of a species of the 
cornus ; the style is about the same length as the petals ; 
• From occidens, the west, being found on the western continent. 
178. First order — Houstouia — Plantain. — 179. Aggregate Sowers — Button-bosh — Corans. 
