360 LYCOPODIALES 
pared with those seen in J/soefes. Here, as in Z. Selago and L. Phlegmaria, 
the hypobasal tier forms the suctorial organ only, and takes no direct 
part in the establishment of the plant. The epibasal tier is like that of 
L. Selago as regards the parts which it initiates and in the positions 
which they severally hold, but differs in its growth in length being 
stunted, and in the early ascendancy of the cotyledon, which condition it 
shares, however, in some measure with Z. Phlegmarta: it differs also in 
the late definition of the apex. But the position of the latter relatively 
to the whole embryo is the same, for the stem originates in close 
relation to the centre of the upper tier of the embryo, as it does in 
all the Lycopods where the embryogeny has been exactly followed. The 
apical cone is small in bulk and late in appearance, these being probably 
correlative consequences of the early advance of the cotyledon. It is 
thus possible to see even in the embryo of Jsoe/es some clear relation 
to the plan which, with such curious modifications, underlies the embryo- 
geny of the Lycopods. 
We are now in a position to enunciate a comparative view of the 
embryogeny as known in the Lycopodiales, and to state it so as to place 
the several curiously divergent types in what is believed to be their 
natural relation to a probable primitive embryogeny. In so doing pro- 
minence is given to the more constant features, while only a subsidiary 
place is given to those characters which are less stable. 
In those Lycopods in which the embryogeny has been exactly followed, 
the embryo consists of a suspensor and two tiers of four cells each 
composing the embryonic body: the two tiers are separated by a wall 
which may be called the “basal” wall (Fig. 182 4, 4). This seems to be 
a general condition, subject only to minor modifications: in Jsoetes, 
however, the suspensor js entirely wanting. In the very various develop- 
ments which follow, the most constant feature is undoubtedly the close 
relation of the stem-apex to the point of intersection of the octant-walls 
in the epibasal tier. In the simplest cases the axis of the embryo is 
thus defined at once as lying between that point and the base of the 
suspensor. The whole embryo is thus primarily a spindle-like body, and 
this may be held to have been the primitive condition for them all. 
But this simple form is subject to early modifications, which disguise 
the position of the axis by delaying its apical growth, and by distorting 
the form: so much so that the position and identity of the apex is liable 
to be lost. The least distorted types are those of Z. Se/ago (Figs. 183, 184) 
and Phlegmaria (Fig. 185), and of .S. spinulosa (Fig. 190), all plants which 
are relatively primitive in their genera as recognised by the characters 
of the mature sporophyte. In Z. Se/ago and Phlegmaria no haustorial 
swellings exist. The early development of the single cotyledon at first 
throws the apex of the axis to one side, but this is rectified later when 
the second leaf appears on the side opposite to the first. The apex thus 
