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EXPLANATION OF THE PLATES. 
Fig. 24. Umbell of what is called the male plant of the 
same, cut vertically and magnified. 
a. The stamens according to some authors, entire, ovoid, 
and sunk into the substance of the umbell. 
b. Other stamens cut vertically, to show their cavity. 
c. Small vascular threads of the stamen, each of which 
abut on a mamilla, or nipplelike eminence, on the surface 
of the umbell. 
Fig. 25. The umbell of what is considered by some as 
the male plant of the same; the upper surface slightly 
concave, with nipplelike eminences. 
Fig. 26. The umbell of what is considered by some as 
the lemale plant of the same ; many-lobed, having the 
fructifications, fig. 20, 21 or 22, beneath. 
PLATE THE TWENTIETH. 
Mosses and Lichens . 
Fig. 1. Tortula muralis. Musci. Entire plant magnified; 
the lemale flower just beginning to appear; surcule short, 
leaves oval lanceolate, terminated with a long hair; peri- 
chsetium 0; bristle terminal ; urn upright, cylindrical. 
a. Ovary, according to some authors. 
b. Style! 
c. Stigma. 
Fig. 2. Fruit of the same, yet young, and magnified. 
a. Calyptra. 
b. Vaginule. 
c. Pedicell beginning to lengthen and separate them. 
Fig. 3. Fruit of the same, more advanced in its growth* 
the calyptra split lengthways, and ready to fall off*. 
Fig. 4. Entire plant of the same, when the pedicel! has 
acquired its full growth, magnified. 
Fig. 5. Urn of the same when ripe, split longitudinally 
and highly magnified. 
a. The urn whose sides are composed of two flakes, the 
external one called sporangium, the internal, sporan- 
gidium. 
b. Seminules contained in the cavity of the urn. 
c . Columella. 
d. Operculum of the urn. 
e. Teeth of the peristome twisted spirally. 
