Embryo in Lilaea subulata , H.B.K . 23 
(Fig. 43) the broad plerome-cylinder of the root is conspicuous, 
and the other tissues at the apex of the root begin to show 
the arrangement found in the fully developed apex. At this 
stage in the specimens examined, no single initial cell could 
be made out for the plerome, whose apex was covered by 
a single layer of periblem-cells which back of the apex 
become divided by periclinal walls. Outside were two layers 
of cells, apparently formed by a periclinal division of the 
original dermatogen, and these give rise to the root-cap. 
In the root of the full-grown embryo, the arrangement 
of the tissues is exactly like that of the roots of the adult 
plant. The plerome-cylinder shows about five rows of cells 
in longitudinal section, the central row being the largest, and 
probably later forming a central vessel. A single cell, some- 
what larger than its neighbours, was seen at the apex of the 
plerome, and may possibly be a single initial, but this point 
needs further examination. A single layer of cells lies 
between the plerome and the root-cap, and this group of 
initials, by the periclinal division of its segments, gives rise to 
the epidermis and cortex of the root. The inner of the two 
layers of cells derived from the primary dermatogen (see 
Fig. 43) becomes the calyptrogen, and from it arise all the 
later layers of the root-cap. 
As the embryo approaches maturity, a second leaf, much 
like the cotyledon, is developed opposite it, and later a third 
one at the base of the cotyledon 1 . In this condition the 
stem-axis has assumed a nearly vertical position, and with 
this displacement of the stem-apex there is a corresponding 
change in the position of the primary root, which comes 
to lie in nearly the same plane as the cotyledon. Hieronymus 
does not figure any intermediate conditions between quite 
young stages and the mature embryo, and to judge from 
his figures (nothing is given on the subject in the text of his 
memoir) he apparently supposed that the origin of the root 
was terminal, as in other Monocotyledons. 
1 See Hieronymus, PI. IV, Fig. 42. 
