176 Shiv Ram Kashyap. — The Structure and Development of 
Embryo. 
The first wall in the fertilized egg is at right angles to the long axis of 
the archegonium. The second wall is at right angles to this and produces 
the quadrants. The octant stage is shown in Fig. 38, where the embryo is 
cut transversely and obliquely and shows four cells. The hypobasal half 
produced by the first wall gives rise to the foot and the root, and the 
epibasal half to the stem and leaf. The foot can be easily recognized by 
the larger size of its cells. It is at first quite small, but in about a week 
Text-fig. 39. 
becomes large (Fig. 39). The young embryo is surrounded by the tissue of 
the prothallus and the neck also has closed above in the meantime. The 
first leaves are usually three in number, but two or four are sometimes 
present as is the case in other species (Campbell). The number of bundles 
in the stem below the first leaf-whorl corresponds to the number of leaves. 
The first shoot shows no cavity in the centre, but all the later branches are 
hollow. The first lateral branch is given off very early and always below the 
first leaf-whorl. It is given off on the side away from the foot and comes out 
by passing under the prothallus. The structure of the hypocotyl at this 
point is still that of the root. Figs. 40-43 show the gradual transition 
from root to stem structure. The figures were drawn from a series of 
sections of the same plant. After the branch-stele has left the main stele 
