478 
Fig. 1. 
10. 
11. 
STRUCTURE AND DEVELOPMENT OF DENDROCEROS. 
EXPLANATION OF THE PLATES. 
PLATE 21. 
Longitudinal section of the apex of the thallus of Dendroceros 
Breutelii(?). X000 (about). The limits of the original segments are 
indicated by the heavy lines. 
. A horizontal section of the apical region 1 of the thallus. The cells x, z' 
are probably both initial cells. — 9, the youngest archegonia; m, the 
midrib. 
. A horizontal section, showing a single apical cell. 
. Transverse section of the upper part of a young archegonium, showing 
four cover-cells. 
. Longitudinal section of a young archegonium, showing the primary 
divisions. X 600. 
. Longitudinal section of a fully-developed archegonium. d, d, the 
cover-cells of the neck. x 600. 
. Longitudinal section of a very young antheridium. Leitz oil-im. ys. 
Oc. 1. 
. A similar section of an older antheridium. . 
. Sections of young antheridia after the segregation of the central tissue 
X 600. a, Longitudinal section ; 5, transverse section. 
Cross-section of the pedicel of a ripe antheridium, showing four rows 
of cells. x 600. 
Longitudinal section of an antheridium, older than those shown in 
fig. 9. 350 (about). 
. Sperm-cells from a full-grown antheridium. X 600. 
PLATE 22. 
Fig. 18. Longitudinal section of a fertilized archegonium with young embryo. 
18. 
19. 
20. 
. An older embryo, showing the archesporium and columella, cof. ; 
x 600. the 
archesporium is shaded. x 300. Il. The first transverse wall in the 
embryo. 
5. Transverse section of a very young embryo. X 600. 
- A similar section of an older embryo. ium 
. Longitudinal section through the base of an older sporogorium, 
showing the differentiation of the sporogenous cells (sp.) and the 
elaters (e/.). x 350. . 350. 
Transverse section near the base of a young sporogonium. X x" 
The archesporium is shaded. 
Upper part ‘of the sporogonium of D. Breutelii, with fully forme! 
spore-tetrads and elaters. X 350. col., columella; sp.» spores; €" 
elaters. 
A single free elater of D. Breutelit. X 390. 
