22 
Lang. — Studies in the Morphology and 
tier destined to develop into the embryo proper and the second tier of the 
suspensor was evident though not so strongly marked ; the terminal tier was 
more developed in the next lower section which missed the upper tier of the 
suspensor. The preservation of the tissues of this embryo was not sufficiently 
good to allow of detailed representation, but the outline is given because it 
affords a truer idea of the shape of the embryo at this stage than does the 
slightly more advanced embryo next to be described. 
The first of the two well-preserved embryos of intermediate age had an 
abnormally long second tier to its suspensor. This had carried the embryo 
proper into the cavity in the prothallus occupied by the base of the success- 
ful plant. The transverse sections of the prothallus cut the embryo 
horizontally, and, since the latter extended downwards and inwards into the 
prothallus, an idea of its shape and construction as a whole could only 
Text-fig. 3. Outline figures of reconstructions of three embryos, x about 30 diameters. 
A, the smaller intermediate embryo seen from the side. B, the larger intermediate embryo seen 
from the side, s 1 , upper tier of suspensor; s 2 , lower tier ; e, embryo proper. The cross is opposite 
the apex of the shoot, c, mature embryo seen from the side on which the suspensor is attached. 
s 2 , suspensor ; f, foot ; r, root ; cot, first leaf ; st, position of apex of stem covered by hairs. 
be obtained by combining the information obtained from the successive 
sections. Text-fig. 3, A shows the shape of the embryo as given by a model 
constructed to scale, the embryo being seen from the side, while outline 
figures of a number of the sections of the region of the prothallus containing 
the embryo are given in Text-fig. 4. Two of the sections are also repre- 
sented in Pl. III, Photos. 3 and 4. As the latter photograph shows, the pro- 
thallus bore a well-developed plant (e 1 ), the embryo under consideration 
(, e 2 ), and the younger arrested embryo already described ( e 3 ). The embryo 
of intermediate age is seen in Text-fig. 4, B-F. In B the large cell forming 
the upper tier of the suspensor (A) is seen cut obliquely, but the level of the 
section is still above the rest of the embryo. In c the lower portion of this 
cell is still seen (s 1 ), and continuing obliquely downwards and inwards from 
it is a row of cells corresponding to the elongated second tier of the 
