THE LIVERWORTS OR HEPATICS 515 
cells each divide into four spores, while the outer cells become some- 
what thickened to form a protective case or capsule (Fig. 338 Q,R, 8). 
At the same time the basal part of the archegonium grows apace and 
may become so thickened as to give additional protection to the 
spores over the winter. When thus developed it is termed a calyp- 
tra.1_ The spores are set free in spring by the breaking down of 
the coverings about them, and they germinate by producing a row 
of cells of which the apical one finally develops a thallus like that 
already described. We have thus in Riccia quite as evident an 
alternation of generations as we found in Coleochete, both the 
oe and the sporophyte being somewhat more highly de- 
veloped. 
— 
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Rg 
=e oe 
oS 
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ae 
Feo 
5 
Ny 
s o 
A > 
r1so—40 
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5 
Fart 
im 
—" 
Fic. 339.—Crystalworts. A-C, Riccia glauca (28°): A, young antheridium; 
st, stalk. B, same, older. C, same, still older, showing the many cells, 
in which motile gametes (spermatozoids) are produced. D, ripe an- 
theridium of R. minima (412); e, outer cells of thallus; l, air-spaces. 
E, R. ciliata (282), growing-tip cut vertically to show the terminal 
cell (s) which by its successive divisions produces all the rest of the 
plant, the pseudo-leaves (b’—b’’”’) which project from the lower surface 
of the thallus and hold water for it, and archegonia, very young (a’) 
and full grown (a’’), ready for fertilization. (Waldner, Kny.) 
Both generations are still more highly developed in the umbrella- 
liverwort (Marchantia, Figs. 340-342), a common species growing on | 
the earth in moist localities. The spores germinate much as in 
Riccia, but the thalli are always bisexual. At first, however, both 
forms are essentially alike and resemble a brood-lobed Riccia. From 
the under side arise numerous unicellular pseudo-roots and many 
scale-like pseudo-leaves. On the upper surface are often formed 
numerous brood-bodies of the form shown in Fig. 342, which are 
produced at the bottom of little cups the whole suggesting a minia- 
ture nest full of eggs. By this peculiar form of vegetative reproduc- 
tion the gametophyte is rapidly multiplied; for as soon as a brood- 
1Ca-lyp’tra < Gr. kalyptra, a veil. 
