336 Campbell. — Studies on the Araceae , III. 
root-tissues, which are not very clearly defined. A distinct suspensor 
cannot be recognized. 
In the young embryo the central cylinder or plerome of the root can 
be distinguished, but its limits are not very clear, and it is quite impossible 
to refer its origin to any definite divisions in the younger embryo. The 
stem-apex is a flat area lying in a deep cleft between the base of the large 
pointed cotyledon, and the short thick root, but the limits of the stem are 
quite impossible to distinguish ; nor at this time is it possible to make out 
any strictly cauline vascular bundle. In the axis of the cotyledon is a 
slender bundle of procambium cells much like that in the root. The base 
of the cotyledon extends around the cleft containing the stem-apex, which 
later becomes completely hidden by the sheath-like base of the cotyledon 
( F >g- ?fi)- 
The embryo grows rapidly, until it finally reaches a length of about 
2 mm. Like various other low Monocotyledons, the embryo is far 
advanced at the time the seed is ripe, but part of the endosperm also 
persists. The second leaf is well developed, and this together with the 
stem- apex is entirely concealed in the cavity formed by the overlapping 
margins of the sheathing base of the cotyledon. The ripe embryo is in 
shape very much like that of Naias 1 i but it does not entirely fill the 
embryo-sac. 
In the mature embryo the young vascular bundles are very evident, 
but no tracheary tissue has developed. Each of the primary organs (except 
the stem) has an axial bundle which unites with the bundles of the other 
organs at their junction. The tissues of the young root (Fig. 35) are 
arranged like those of certain other Monocotyledons, e. g. Sparganium. 
The root-cap is clearly separated from the tissues beneath, and has its 
own initial cells, which are quite independent of those of the other primary 
tissues of the root. There is an evident plerome-cylinder, between which 
and the root-cap is a single layer of cells serving as the initial for both the 
epidermis and plerome. The outer cells derived from this common initial 
layer divided by periclinal walls, the outer cells forming the epidermis of 
the root, the inner ones, which also undergo further periclinal divisions, 
contributing to the growth of the periblem or cortical tissues. 
The presence of acicular crystals of calcium oxalate is a marked 
characteristic of most Araceae, and these are found to be present in 
considerable numbers in the embryo of Anthurium . These crystals are 
formed in compact bundles in special cells distinguished by more granular 
contents than those of the neighbouring cells (Fig. 37). They also have 
larger nuclei, which sometimes show indications of degeneration. 
As the seed ripens there is the usual accumulation of reserve-food, 
1 Campbell, A Morphological Study of Naias and Zannichellia. Proc. Calif. Acad. Sciences. 
Third Ser. Bot. I, No. 1, 1897. 
