40 
NOTES ON YORKSHIRE BRYOPHYTES. 
IV. Frullania and Jubula. 
(Continued from page 16.) 
F. CAVERS, D.Sc., F.L.S. 
Professoy of Biology, Hartley University College, Southampton. 
THE sequence of the cell-divisions in the development of the 
sporogonium is extremely regular in /yu//anza,* and has been, 
on the whole, correctly described and figured by Hofmeister, 
Kienitz-Gerloff, Leitgeb, and Leclerc du Sablon. The first 
wall in the fertilised egg-cell is transverse to the long axis of 
the archegonium, and the lower cell (Aypobasal) then divides 
by a vertical wall, while the upper cell (epzbasa/) divides trans- 
versely (Fig. 6, G). Each of the two upper cells then divides 
by two sets of vertical walls that cut each other at right angles. 
In the meantime, the two hypobasal cells have divided again by 
vertical walls, so that the embryo now consists of three tiers, 
each having four nearly equal cells. In some cases I have 
found one or more (as many as three in a few cases) further 
transverse divisions in the epibasal half of the embryo before the 
appearance of the vertical walls; this is normally the case in 
other /ungermanniacee. The hypobasal cells soon project 
from the surface and divide rather irregularly, forming the 
blunt foot which presses into the tissue forming the stalk of the 
fertilised archegonium. The cells of the uppermost tier divide 
by tangential walls into four inner cells, which have denser 
protoplasm than the outer ones, and which form the arche- 
sporium, while the four outer cells produce the wall of the 
capsule. The tier of cells between capsule and foot divides by 
longitudinal walls, which separate eight outer cells from four 
inner ones; this tier forms the seta or stalk of the capsule. 
The four primary archesporial cells divide repeatedly by 
longitudinal walls, resulting in the formation of a lens-shaped 
layer of about two hundred cells, the central cells being longer 
than the marginal ones (Fig. 6, G—L). These cells then be- 
come differentiated into two sets. Some of them divide 
transversely so as to produce rows of cells; the others grow in 
length, but remain undivided, forming long cylindrical cells 
attached to the inner surface of the capsule wall above, and to 
the floor of the capsule below (Fig. 6, K L). The rows of 
* The details of development of antheridium and archegontum are 
omitted from this paper, since they do not differ from the normal process in 
other liverworts. See Scott, ‘Structural Botany,’ Part 2; Campbell, 
*‘Mosses and Ferns,’ 2nd Ed. 
Naturalist, 
