18 Principles of Classification . 
stamens are united by their filaments and form a tube 
as seen at a. 
Plate 3 . fig. 17 . Diadelphia class in which the sta- 
mens are divided into two bundles as at a ; one stamen 
only in one division. Fig. 18. Polyadelphia having the 
stamens divided into more than two bundles as at a. 
Fig. 19. Syngenesia class, with compound flowers ; a, one 
of the flowers separated ; b, the common receptacle. 
Fig. 20. Gynandria class, in which the stamens are plac- 
ed on the top of the pistil as at a. Fig. 21. Moncecia 
class, in which the stamens and pistils are in separate 
flowers on the same plant ; a. a. flowers with stamens ; 
h, b, flowers with pistils. Fig. 22. Dicecia class, in 
which the flowers with stamens and pistils are on sepa- 
rate plants ; a, flowers with stamens ; b , flowers with pis- 
tils. Fig. 23. Polygamia class, in which three kinds of 
flowers are found on the same plant ; a, flower with sta- 
mens only ; b , flower with pistils only ; c , flower with 
both stamens and pistil. Fig. 24?. Cryptogamia class, in 
which the parts of fructification are not distinctly seen. 
Inflorescence.-— The inflorescence, or mode of flower- 
ing, that is, the distribution of the flowers on plants, 
affords useful discriminating marks, and of these differ- 
ent kinds have received appropriate names. 
When the flowers surround the stem in a kind of 
ring, it is called verticillus, or whorl, as in dead-nettle 
and wild marjoram. 
A cluster, or raceme, racemus, is composed of nu- 
merous rather distant flowers, each having its own pro- 
per stalk, but all arising from a common stalk, as in red 
currants. Solanura dulcamara, bitter sweet, exhibits 
an example of a compound raceme ; and actcea race- 
