EMBRYOLOGY 359 
other parts originate from the epibasal tier: the cotyledon with its ligule 
is the first part to be organised: it is followed soon by the first root, 
which arises at the opposite side of the epibasal tier to the cotyledon 
(Fig. 191 C, D, E, F). Between these parts a slight depression is formed, 
and it is surrounded by a semicircular ridge: within this the apex of the 
axis is at last organised, and it soon gives rise to the second leaf, which 
Fic. 191. 
Jsoetes echinospora, var. Braunit, Dur. xX 365. A=an archegonium. B=a two- 
celled embryo within the archegonium. D, 2, #=three successive horizontal sections 
of a somewhat advanced embryo; R=root ; cot=cotyledon; st=stem; /=ligule. x 175. 
C=median longitudinal section of a young embryo; /=ligule. x 200. G=median 
section of a young sporophyte with second leaf, 2, already formed; 7,=second root; 
st=stem apex. xX 150. (After Campbell.) 
faces the cotyledon: the very exiguous apical cone lies between them 
(Fig. 191 G). And so the shoot is established, bearing successive leaves 
with spiral arrangement, and successive roots, of which the second is below 
the base of the second leaf. 
Comparing this apparently divergent embryogeny with that of the 
‘Lycopods above described, if the whole embryo be imagined inverted 
in its orientation relative to the archegonial neck, and their suspensor 
be imagined entirely away, then the two embryonic tiers may be com- 
