Anacrogynous J unger manniales. 205 
walls, but in Podomitrium these cells are uniformly thickened and 
bear no definite fibres ; in both genera there arise from the bottom 
of the capsule cavity isolated fixed elaters of varying form, some being 
short and without fibrous thickenings, others long and elater-like. 
In Aneura the developing sporogonium is protected by a massive 
and fleshy calyptra formed by vigorous growth of the tissue of the 
female branch ; this active growth extends to the tissue underlying 
the fertilised egg, where a projecting bulbous mass is formed, 
bearing rhizoids. The calyptra carries up the scales which 
grow out around or among the archegonia, and usually also the un¬ 
fertilised archegonia themselves. In Metzgevia the calyptra is not 
so massive, and is formed chiefly from the venter of the fertilised 
archegonium. 
In the Aneuraceae, asexual reproduction is effected in various 
ways. The simplest is the separation of ordinary branches by the 
dying away of the old portions of the thallus ; in Podomitrium and 
Umbraculum the severance of the branches from the parent axis is 
facilitated by the fact that the strand of thick-walled cells in the 
ventral branch is not continuous with that in the parent stem. 
The asexual reproduction of Metzgevia by means of gemmre has 
recently been investigated by Evans (15), who has shown that each 
of these bodies (consisting usually of a single layer of cells) arises 
from a single cell of the parent thallus, either from a cell of the 
wing or from one of the cortical cells of the mid-rib. The super¬ 
ficial cell about to produce a gemma projects beyond its neighbours ; 
the outer wall of the cell is ruptured, but the protruding protoplast 
becomes covered by a layer of gelatinous material which probably 
represents a modification of the inner part of the original outer wall 
and which is deposited prior to the rupture of the wall. The pro¬ 
jecting cell thus formed, either with or without a preliminary division 
into a lower cell which does not enter into the formation of the 
actual gemma, usually undergoes at once divisions which cut out a 
two-sided apical cell ; in some cases the gemma has two growing- 
points from the earliest stages of its development. The details vary 
greatly in different species, as shown by Evans. 
In several species of Aneura, gemmae are formed in a somewhat 
different manner. The contents of a superficial cell of the thallus 
separate from the wall, and the rounded-off protoplast acquires a 
cell-wall and divides into two cells. The two-celled gemma escapes 
by rupture of the free outer wall of the mother-cell. As compared 
with Metzgevia, the further development of the gemma in Aneura is 
deferred until after the gemma is set free. 
