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Thallus y to y z inch wide, not cilliate at margins, entire or lobed 3. 
3. Thallus simple or only once forked, 1 to 4 inches long, prostrate; margins 
sinuate to entire; capsule ovoid-cylindric Pallavicinia. 
Thallus dichotomously branched, y to 1 y z inches long, often densely clus- 
tered and ascending, margins lobed: capsules spherical without perianth, 
appearing buried in the midrib for 
some time before the ripening of spores 
(Fig. 7) Blasia. 
4. Thallus pinnately orpalmately branch- 
ed, 1/24 to 1/12 in wide (except 
R. pinguis) Riccardia. 
Thallus subsimple or dichotomously 
branched, to y inch in width (Fig. 
8) Pellia. 
Fig. 7. 
Fig. 8. 
Fig. 7. Blasia pusilla L. a. Fertile plant in August 
showing capsule in position. At the side is shown the cap- 
sule removed from the thallus. b. Sterile plant with flask- 
shaped bodies which produce gemmae. 
Fig. 8. Pellia epiphylla Raddi. Thallus X 1, showing 
involucre and position of capsule as it appears in August. 
THE SCALE MOSSES (JUNGERMANNI ACE/E). 
The reproductive part of the Scale Mosses, including the ripened cap- 
sule and its connected parts, perianth, involucre, etc., is essentially as in 
the Thalloid Scale Mosses, but the vegetative part strongly resembles the 
true mosses in general appearance. The leaves, however, are apparently 
flattened out into two rows, one on either side of the stem. They are 
entirely without midrib and are frequently two-cleft or lobed. One of the 
lobes is often smaller and folded under the other making the leaves “ com- 
plicate-bilobed,” in the language of the books as shown in the illustrations 
of Radula and Porella. This can best be made out by holding a single 
stem up to the light and examining with a lens, when the under lobe will 
show plainly as a deep shadow. In Scapania, the under lobe is the larger 
and the plants look as if there were four rows of leaves. The lower lobe is 
called the lobule and the upper simply the lobe. Very many species have a 
third rows of leaves on the under side of the stem called technically “ amphi- 
gastra” or underleaves, these vary in size from one-third the size of the 
ordinary leaves to so minute that high powers of the compound microscope 
are needed to see them clearly. The upper margin of the leaves may over- 
lap the lower margins of the leaves next above as in Porella, or the upper 
margin of a leaf may lie under the lower margin of the leaf next above as 
in Plagiochila. In the former case the leaves are said to be incubous, in 
the latter succubous. As this distinction is in most cases easy to observe, 
it is given a prominent part in the key. Occasionally the leaves are so far 
apart that it is hard to determine the leaf arrangement, but a careful search 
