A natomy of the Opkioglossaceae . 2 1 
was contained, served however to indicate its shape and its relation to 
the archegonial venter in which the fertilized egg originally lay. Such 
a young arrested embryo as is shown in PI. Ill, Photo. 1 may be com- 
pared with Bower’s figures of the young embryo of Botrychium obliqumn. 
The wider end next the surface of the prothallus marks the position of the 
enlarged archegonial venter ; the still undivided embryo has broken through 
the lower limit of this and is extending deeper into the prothallus. The 
embryo shown in Photo. 2 was somewhat older when its growth was 
arrested ; its position in the prothallus is seen in Photo. 4 at e 3 , In 
this case also the position of the archegonial venter is recognizable above, but 
the embryo had extended more deeply into the prothallus. The tissues of 
the embryo are broken down, but the mass in the lower end of the cavity 
showed the presence of a number of nuclei, and represented the embryo 
Text- fig. i. Young atrested embryo consisting of three cells in longitudinal section, ar, 
archegonial neck ; j 1 , upper tier of suspensor; s 2 , second tier of suspensor; e, the embryo proper. 
X 20G. 
Text-fig. 2. Older arrested embryo cut horizontally, f, foot of the plant borne on the same 
prothallus ; ar , archegonial neck above the embryo ; j 1 , upper tier of suspensor ; s 2 , lower tier ; 
e, embryo proper. The broken-down tissues of the embryo are not indicated, x 50. 
proper. Segmentation had thus considerably advanced before this embryo 
perished. The walls separating the three tiers of the embryo (P, P, e) were 
not preserved. They are shown, however, in Text-fig. 1, which represents 
an embryo intermediate in age between those in Photos. 1 and 2. It 
is unnecessary to go further into the features of these very young arrested 
embryos, a considerable number of which were studied. They showed the 
similarity of the early stage of development to Botrychium obliquum , and 
they indicate that the region of the suspensor is distinguished from the rest 
of the embryo at an early period, but they do not justify inferences as 
to the early stages of segmentation of the embryo proper. 
The older arrested embryo, a horizontal section through which is 
represented in Text-fig. 2, showed the upper tier of the suspensor marked off 
by a thick wall from the second tier, while the limit between the terminal 
