264 BRYOPHYTA 
B. THe JUNGERMANNIALES. 
The same principle is illustrated also in the Jungermanniales, but with 
differences of detail. In these the first segmentation of the zygote 
separates a hypobasal cell, which in some cases develops as a multicellular 
Fic. 124. 
Frullania dilatata, development of the embryo. X300. (After Leitgeb). -r, x, the 
archeSporial cells. The numbers indicate the primary transverse divisions. (From 
Campbell, Mosses and Ferns.) 
haustorium (/7ud/ania), but more frequently remains as a minute appendage 
at the base of the fruit, while the epibasal cell gives rise to the capsule, 
stalk, and foot. So far as a comparison on the basis of the segmentation 
of the zygote is valid, this would indicate in the Jungermanniales a still 
further delegation of function from the 
hypobasal to the epibasal half of the 
embryo. 
The epibasal half of the zygote under- 
goes segmentation, so that a number of 
transverse discs are formed, each composed 
of four cells, while the terminal tier is 
composed of four octants of a hemisphere 
(Fig. 124). The segmentation is often 
: very regular, but exceptions exist.! The 
Fic. 125, uppermost tier of cells appears to be cut 
Embryos of Radula complanata. x23. Off by the first transverse wall in the 
(After Leitgeb.) 7, 8, show the basal ap- F - 
pendage cut off by the first segmentation of epibasal half of the zygote, and in many 
ae eeiced embryo PPerFesion of 2 Of the Anakrogynous Jungermanniaceae 
the whole of the capsule is derived from 
these cells: subsequent intercalary divisions in the lower half of the 
epibasal cell gave rise to the sterile seta. But, on the other hand, in many 
of the Akrogynous Jungermanniaceae—for instance, in Radu/a—it is shown 
by Leitgeb? that some of the lower tiers of cells also take part in the 
formation of the capsule; in Aadu/a the number of these appears to be 
three (Fig. 125). Thus there is in such cases no general distinction, on 
"See Campbell’s Figs. ‘of Porella; Mosses and Ferns, Fig. 55. 
2 Lebermoose, ii., p. 55. 
