Campbell . — Studies on the Araceae , III \ 335 
usually, perhaps always, followed by a second transverse wall before any 
vertical walls are formed. 
The next divisions probably vary somewhat, to judge from the varying 
appearance of the later stages which were found. In most of these there 
was evidence of intersecting vertical walls in the second and third of the 
three primary segments of the embryo, so that a longitudinal section shows 
the second and third segments divided by a median wall into two equal 
parts. This quadrant division may also occur in the small basal segment, 
which forms a very rudimentary suspensor, but this does not seem to be 
always the case. 
In most instances the embryo assumes a nearly globular form, less 
commonly (Fig. 25) it is somewhat elongated, with an absence of the usual 
quadrant formation. The rudimentary suspensor is apparently of little or 
no importance as an organ of absorption, but remains very much reduced 
as in other Araceae that have been studied. This absence of a functional 
suspensor is accounted for by the early investment of the young embryo 
by the endosperm-cells with which it is in intimate contact from the first. 
As the embryo enlarges, its original globular form is somewhat altered, 
the basal part becoming a little flattened and the whole embryo assuming 
a slightly conical form (Fig. 27); but as yet there is no evidence of the 
differentiation of the organs of the young plant, nor of its permanent 
tissues. The evidence of the quadrant divisions in the young segments 
of the embryo is still more or less apparent, but the tissues are still entirely 
similar, and except for a superficial layer of cells constituting the young 
epidermis, the tissues are quite undifferentiated. 
Owing to the great uniformity of the tissues, it is not possible to 
decide with absolute certainty the relation of the organs to the primary 
divisions of the embryo. The latter becomes elongated, assuming a 
slenderly conical form, and there is formed at one side a depression which 
marks the position of the stem-apex (Fig. 29, a), whose origin is thus seen 
to be of the characteristic monocotyledonous type. It is quite impossible, 
however, to say whether its position corresponds in any way to the early 
divisions of the embryo. 
About the same time that the stem-apex is first visible the differ- 
entiation in the root-region begins. A clearly defined line, marking the 
boundary of the root-cap, can be seen (Fig. 29, a), this line probably corre- 
sponding to the second transverse division in the young embryo, although 
this point could not be determined with absolute certainty. If this is 
correct it means that everything except the rudimentary suspensor and 
the root-cap is derived from the terminal segment of the young 
embryo. 
A section of the embryo at this stage shows the root-cap ( r.c.)> which is 
lenticular in form, separated by a sharply marked boundary from the other 
