48 Cavers : Notes on Yorkshire Bryophytes. 
The divisions in the seta are very regular, and in cross 
sections there is seen a central group of four cells covered by 
three concentric layers of cells (Fig. 7, B). The seta is not so 
sharply marked off from the capsule as is usually the case in 
liverworts, for at the base of the capsule there is a mass of thin- 
walled tissue which may, as suggested by Spruce, be regarded 
as corresponding to the hypophysis or expanded upper part of the 
seta found in many mosses. Hence, when dehiscence occurs, 
the four valves of the capsule wall do not become free right 
down to the point of junction with the cylindrical seta, and 
Frullania capsules are usually described as opening for only 
about two-thirds of their length. 
The calyptra, formed by the active growth of the fertilised 
archegonium, becomes five or six cells thick, and is raised on a 
massive stalk, leaving the unfertilised archegonium at the base 
(Fig. 6, E). The old archegonium neck at the top of the 
calyptr.i can be seen inside the perianth (Fig. 8). 
The opening of the capsule has been accurately described by 
Goebel.* The capsule wall splits from above, downwards, into 
four valves, which spring backwards so as to lie almost 
horizontally at first, each valve carrying with it a share of the 
elaters and the rows of spores lying between them. Just before 
this, while the whole capsule is drying, the elaters contract, and 
their lower ends become free from the floor of the capsule, while 
the more firmly fixed upper ends remain attached to the inner 
surface of the capsule wall. The whole process is due to the 
shrinking of the membranes in the capsule wall and in the 
elaters; when elaters from a dehisced capsule are placed in 
water they elongate again, and the spiral band becomes more 
loosely coiled. The spores are discharged with great force, and 
may be thrown out to a distance of three or four inches, so that 
the act of dehiscence might well be termed an expiosion, quite 
different in degree, though not in kind, from the process 
observed in other liverworts, and in a few seconds from the 
rolling back of the valves the exploded capsule shows only a 
few spores that have remained entangled between the elaters. 
It is difficult to analyse this sudden action, but it is possible 
that the elaters themselves bend or twist on being set free at 
their lower ends, in addition to being passively moved outwards 
with the valves, and causing the spores to be jerked out. 
The earliest divisions in the germinating spore take place 
* “ Flora,’ 1895, Heft 1. 
Naturalist, 
