1922] DUPLER—REBOULIA 155 
and becomes exposed, excepting where covered by the receptacle 
tissue, which has grown downward and formed an involucre about 
both calyptra and sporophyte, dorsally and laterally. 
Discussion 
The finding of filamentous embryos in an increasing number of 
Marchantiales makes it evident that the octant type of embryo is 
not necessarily the rule in this group, in contrast with the filamen- 
tous embryo of the Jungermanniales. This, together with the occur- 
rence of oblique walls and even a triangular apical cell, tends to 
bring the Marchantiales and Jungermanniales closer together as 
regards their embryogeny, and in an occasional partial agreement 
with that characteristic of the Musci. 
In a previous paper, the writer (6) referred to the plasticity of 
Reboulia as shown by the male reproductive structures. ‘The varia- 
tions found in the development of the embryo give additional sup- 
port to that view. 
In the differentiation of the capsule region from the foot and 
stalk, Reboulia is probably like that of most Marchantiales, in that 
the capsule is generally derived from the epibasal half of the egg. 
Even in Reboulia there is no absolute proof that the epibasal cell 
may not contribute in part to the stalk region, as is the case in the 
Jungermanniales. The behavior of the basal cell of the filament is 
suggestive of an approach to the situation in some of the Junger- 
manniales where the entire hypobasal cell is a mere appendage to 
the embryo. 
Summary 
. The mature egg and early embryo are elongated, slightly 
caved bilaterally symmetrical bodies. 
2. Fertilization takes place in October, the development of the 
embryo beginning at once, the sporogenous tissue becoming dif- 
ferentiated by winter, the sporophyte maturing in May and June. 
3. The early embryo shows considerable variation in its develop- 
ment, the chief features being: (1) the first division of the egg may 
be transverse or oblique; (2) transverse division of both hypobasal 
and epibasal cells results in a filamentous embryo of four cells; 
