446 BOTANICAL GAZETTE [JUNE 
slight movement of the cover glass will usually serve to dislodge them. 
This loose union along the sides of the cells as they are joined to 
make up the peridial tissue, tends to make the peridium rupture at 
its maturity by longitudinal slits along the sides rather than at the 
apex, and gives the lacerated and fimbriated appearance so char- 
acteristic of most of the species. Only two species of the true Roes- 
telia type have been observed which have peridia that do not become 
more or less split up; these are R. Harknessiana E. & E., an unattached 
species from California, and 
G. inconspicuum Kern (R. 
Harknessianoides Kern), from 
the western mountain region. 
In these the peridia are firm 
and remain tubular even after 
months of weathering. 
The way in which the cells 
are joined end to end is another 
Fic. 1.—Showing how the cells of some distinctive feature . ba 
species are joined end to end; the portions 8fOUD. In addition to being 
uppermost are toward-the apex of the perid- | imbricate, a character common 
ium; ing the outer wall of the upper cell to many aecial forms, the ends 
a sor perience oes of the cells are, with a few 
possible exceptions, articulated 
in such a manner as to make movable joints (text fig. I). This 
power of yielding at these joints permits the ruptured peridium to 
curl and twist in a manner particularly prominent in some of the 
species, 
In shape one finds a considerable variety. In some species the 
cells are long and thin (figs. 7, 12), in others short and very stout 
(figs. 8, 15, 16). With respect to shape, it is necessary to consider the 
cells from two points of view, viz., side view and face view. The 
side view, which is the longitudinal radial view, shows the dimensions 
of length and thickness. In this view the outer and inner walls are 
practically parallel. In some of the species which have short and 
rather thick cells, the imbrication at the ends gives an oblique effect 
which makes a rhomboidal shape (figs. 15, 16). Where they are 
longer and thinner, the length becomes more pronounced, and lineat- 
WA 
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