Principles of Classification . 
IS 
Linnaeus added a sixth order, Monogamia, in which the 
flowers are not compound, but single, as the word de- 
notes ; but as the union of the anthers is not always 
uniform, the plants belonging to this order have been 
arranged by later botanists under other classes, accord- 
ing to the number of stamens. 
In the 20th, 21st, and 22d classes the orders are 
formed from the number of stamens, or from the cha- 
racter of some of the preceding classes. 
Polygamia, the 23d class, includes three orders, 
formed upon the principles of the classes immediately 
preceding. 1. Moncecia, in which flowers with both 
stamens and pistils, or flowers with pistils, or stamens 
only, grow on the same plant. 2. Dicecia , when two 
or three kinds of flowers appear on two separate 
plants. 3. Tricecia, in which the different flowers just 
described grow on three separate plants, of which the 
fig furnishes an example. 
The 24th class, Cryptogamia, was divided by Linnaeus 
into four orders, namely, ferns, mosses, flags, and mush- 
rooms ; but Dr Smith has added a fifth order. 1. Fi~ 
licesy or ferns, in which the fructification appears on the 
back, summit, or near the base of the leaf, which is de- 
nominated a frond. 2. Musci, or mosses, which have se- 
parate leaves, and often a stem, and are furnished with 
a calyptra, or hood-like corolla. 3. Uepaticce, or liver- 
worts, having the leaf and stem united, forming a frond, 
but the capsules do not open with a lid as in the mosses. 
In the 4th order, Algce? or flags, the herb is a frond, 
and the seeds are imbedded in its substance, or in the 
disk of a peculiar receptacle. 5. Fungi , or mushrooms, 
have no leaves, and the fructification is in a fleshy sub- 
stance. 
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