EMBRYOLOGY 469 
peculiarities he describes as other than. extreme modifications along the 
lines already indicated by the less specialised embryos of the family. 
The first detailed description of the embryo in any of the species of 
Botrychium was given by Jeffrey for 2B. virginianum, and it has been 
verified in many points by Campbell. The very large prothallus bears 
its archegonia on the upper surface : after fertilisation the zygote enlarges, 
and divides first vertically to the axis of the archegonium, and in the 
hypobasal and epibasal hemi- 
spheres the usual octant 
divisions appear; but these 
segmentations are obscured 
by the less regular divisions 
which follow. The embryo 
thus appears as an ellipsoid 
body, in which no apical 
cells are at first defined. 
Jeffrey states that the whole 
hypobasal hemisphere goes 
to form the foot, while the 
stem-apex and the _ root 
originate from the epibasal 
half: and his drawings cer- 
tainly seem to bear this out 
(Fig. 261). The apical cell 
of the stem (a) is defined 
before the cotyledon appears : 
this is formed on the side Botrychium Lunaria, L. 36=fertilised archegonium; 37= 
é zygote, showing the first segmentation ; 38=embryo of four cells ; 
of the axis next to the root 39-40 embryos cut in direction of the axis of the archegonium ; 
(4), and Jeffrey records that tigen Ute: geen), Se eee 
it is derived from the shoot- 
meristem. It grows rapidly, and finally becomes expanded above ground 
as the first assimilating leaf. Thé root is, however, the first part of the 
embryo to emerge, and a second and third root may make their appearance 
before the cotyledon unfolds: subsequently successive spirally: arranged 
leaves are formed on the axis, but the earliest fertile spike observed in 
this species was borne on the ninth leaf. 
Fic. 262. 
1This interpretation of the data of Campbell differs widely from his own. It is 
impossible here to enter into any full discussion of the question. It should be stated, 
however, that Campbell’s own view is that the type of embryo of O. moluccanum is 
probably the most primitive, and shows an embryo in which no axis exists at first ; he 
regards the definitive sporophyte as a secondary structure developed as a bud upon the 
primary root. In O. pendulum, also, the leafy sporophyte is secondary, neither stem-apex 
nor leaf being produced from the embryo itself (/.c., p. 183). In fact, Campbell takes 
as the most primitive forms those which are most divergent from the type of embryo 
which is usual in other Pteridophytes. It would seem more satisfactory, however, in so 
specialised a case as this, to start from the least divergent, such as O. vzdgataum. 
