24 
Lang . — Studies in the Morphology and 
contrasts with it in the meristematic character of its densely stained cells. 
Although the initial cell of the stem could not be distinguished with cer- 
tainty, it is clear that the embryo of Helminthostachys conforms to and 
supports Bower’s generalization that the apex of the shoot is initiated 
close to the centre of the epibasal pole. 
From this single specimen it is not possible to speak with certainty as 
to the segmentation of the embryo, but careful study suggests the following 
interpretation, which is consistent with the appearances presented by both 
younger and older embryos. The first transverse wall evidently separated 
the cell forming the upper tier of the suspensor from the rest of the embryo. 
The next wall was also transverse and separated the second tier of the sus- 
pensor from a terminal cell giving rise to the embryo proper. The embryo 
proper has increased markedly in size as compared with the suspensor, and 
has undergone differentiation into two tiers which are comparable to the 
epibasal and hypobasal tiers of other embry os whether provided with suspensors 
or not It is not clear whether the separation of these two tiers was 
effected by the first transverse wall in the terminal cell or was deferred until 
after longitudinal division. 
There is no reason to doubt that the foot is developed from the 
hypobasal tier, and the shoot including the stem-apex and first leaf from 
the epibasal tier. Reasons will be given later for believing that the first root 
is also derived from the epibasal tier. The root is certainly not differentiated 
at this stage, but the stem-apex is commencing to be depressed and the first 
leaf may be defined, though it was not distinguishable. 
The second embryo of intermediate age was considerably larger than 
the one just described, and showed the first appearance of vascular tissue. 
Its shape as reconstructed is represented in Text-fig. 3, B ; the upper tier of 
the suspensor (k 1 ) consisted of a single large cell, the second tier ( s 2 ) was not 
unduly elongated as in the preceding example, and widened gradually 
towards the embryo proper. Both tiers of the latter had contributed to the 
enlargement of the embryo, but the apex is still not directed upwards, 
its position being indicated by the cross. 
The position of the embryo in the prothallus, which also bore a well- 
developed plant, and the plane in which the embryo was cut will be evident 
from Text-fig. 5. The plane of section in this case was practically at right 
angles to the long axis of the embryo. Starting from the back of the embryo 
below the remains of the archegonial neck, the series first showed the large 
cell forming the upper tier of the suspensor (Text-fig. 5, A, s l ). This joined 
on at the lower end to the second tier of the suspensor (s 2 ), which was com- 
posed of a tissue of rather large cells and widened gradually to its junction 
with the base of the embryo proper (e). The second tier of the suspensor 
is seen in B joining on to the lower end of the upper tier ; in C the 
second tier of the suspensor is seen above, while below it the section 
