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CLASS DIADELPHIA. 
LECTURE XXXIV. 
CLASS XVI DIADELPHIA. 
This is the class of two brotherhoods, the stamens being uni- 
ted by their filaments into two sets. The flowers of this class 
have already been described under the head of Papilionaceous, 
which you will recollect means butterfly shaped ; this peculiar 
form of their corollas is an important mark of distinction in 
this class. 
There are, however, two circumstances to be noted here, in 
order to prevent you from falling into error with respect to this 
class. 
1st. There are some plants here which have their filaments 
united in one set ; where a flower is papilionaceous, it is 
still kept in this class although there may be no apparent 
division in the brotherhood or set. 
2nd. Although the flower be papilionaceous, and has ten sepa- 
rate stamens, it is placed in the 10th class; this is the case 
with a few genera ; as the cassia and wild indigo. This 
circumstance was remarked under the tenth class. 
The distinction of the filaments into sets is often somewhat 
difficult to be ascertained ; in the pea for example, it is necessary 
to take a pin, and separate the filament which is alone, in order 
to perceive that it is not united to the other nine filaments. 
When they are separated, it is mostly in this way, with nine 
filaments together, and one which seems disconnected ; there 
are but few examples of stamens being arranged in equal sets of 
five each. 
, The nature of the fruit in the papilionaceous plants is legu- 
minous, or bearing a pod, like the bean and pea, called a 
legume. 
The orders in this, as in the preceding class, are founded up- 
on the number of stamens, the class not having appropriated to 
itself a character drawn from the same circumstance. 
PENT-OCTANDRIA. 
We could not expect from the character of the class, “ sta- 
mens united into two sets,” to find any plants with but 1 stamen; 
therefore there is no order until we find some plants which an- 
swer the classic character. Those with five or eight stamens 
are all placed in one order called Pent-octandria, (five and eight 
Class Diadelphia — Two circumstances to be noted — Flowers Papilionace- 
ous — Fruit leguminous — Order Pent-Octandria. 
