32 
Latig. — Studies in the Morphology and 
The nature of this complete readjustment of the organs of the embryo 
of Helminthostachys during the curvature must be borne in mind in com- 
paring it with embryos (such as that of Danaea ) in which the axis remains 
straight throughout development, and the foot shows no marked enlarge- 
ment. 
If the embryo of Helminthostachys is compared with what we know of 
the embryo of Botrychium obliquum 1 it will be clear that here also the first 
direction of development was in a line directly inwards from the archegonial 
neck, and that later a change in direction of the growth of the embryo 
proper led to the shoot growing vertically upwards and the root vertically 
downwards. The root and shoot of the fully grown embryo are in the same 
straight line, and it is noteworthy that no well-developed foot is described 
in this plant. With our present imperfect knowledge it must remain an 
open question whether the suspensor as figured by Lyon has two tiers, and 
corresponds exactly to the suspensor of Helminthostachys , or whether the 
second tier in his figure corresponds to the poorly developed hypobasal 
half of the embryo proper which in Helminthostachys forms the foot. 
In the other species of Botrychium and in Ophioglossum there is no 
suspensor, the embryo is inverted from the first, and the primary distinction 
is into the hypobasal half directed downwards into the prothallus and 
forming the more or less marked foot, and the epibasal half directed 
towards the archegonial neck and forming all the organs of the plant. It is 
not necessary to enter into detailed comparisons with these forms, and 
reference may be made to the works of Bower and Campbell cited. 
It is difficult to discuss any one peculiar pteridophytic embryo without 
being led into a general survey of the embryogeny in the phylum. To 
avoid this the comparative discussion in Chapter XLII of Bower’s ‘ Land 
Flora ’ may be assumed as a starting-point. This is the more justifiable, as 
this chapter may be regarded as the first critical comparative statement on 
the morphology of the embryo of Pteridophyta. 
Professor Bower regards the relation of the apex of the axis to the 
primary segmentation of the embryo as constant, and the apex of the stem 
as occupying as nearly as possible the centre of the epibasal hemisphere. 
Whatever subsequent change in the direction of the apex occurs, the 
polarity has been determined before, and is indicated by, the first segmen- 
tation of the embryo. All further knowledge of particular embryos since 
the date when Professor Bower made this generalization seems to confirm 
it, and it appears to state a primary fact. 
Within the same phylum, as Professor Bower further points out, 
examples of embryos with suspensors and embryos without suspensors are 
physiological problem thus raised is when and how the internal correlative influences between the 
embryo and the prothallus (or seed) are superseded by this irritability of the parts of the embryo to 
gravity. 
1 Cf. the figures in the Land Flora, pp. 471, 472. 
