268 Farmer. — On the Embry ogeny of 
posterior pair of hypobasal octants, beneath the stem ; its 
cells which border upon the prothallium afford a good 
example of digesting and absorbing cells : their contents and 
general appearance contrasting strongly with those of the 
surrounding prothallial cells. 
The root is formed from one of the octants beneath the 
cotyledon, that is from an anterior hypobasal one. The sister 
octant merely undergoes a few irregular divisions and rounds 
off the embryo on that side. The root is first indicated by 
a triangular apical cell, and is best seen in sections cut at 
right angles to the basal and median walls. It offers con- 
siderable difficulty in tracing out the course of its further 
development, as the apical cell which is at no time very clear, 
is subsequently replaced in most cases by a group of initials 
(see Fig. 8), as I convinced myself by an examination of a 
number of sections specially cut obliquely, in order to deter- 
mine this point. In some instances however I was unable to 
satisfy myself that a cell-group was formed at the young root- 
apex, and there seems no doubt that some variability exists 
in respect of the structure of the latter. This is well shown in 
the Figs. 13-17, which were drawn from transverse sections of 
the roots of young plantlets in which not more than two 
leaves had been found. It may easily be seen that not only 
does the number of apical cells vary, but also the direction of 
the early division-walls is very inconstant, even giving rise in 
one case (Fig. 15) to an appearance almost suggesting the 
presence of an apical cell. It is obvious however that this 
construction would break down if the attempt were made to 
derive the daughter-cells from such a supposed cell, even in 
the section figured, which was one most favourable to such a 
hypothesis. Possibly a connection may exist between the 
relative robustness of the root and the structure of its apex, 
and this may perhaps account for the discrepancies existing 
in the statements given by different authors. I regret that 
my own material was not sufficient to determine this point 
conclusively in the case of the young embryos, but we know 
that some latitude of variation exists in certain ferns, e. g. 
