3 76 Holm. — On O bo /aria virginica . 
phyll in the leaves shows that it is able to provide its own 
starch, and this fact seems sufficient to prove that our genus 
is neither parasitic nor saprophytic. It is also true that the 
root- system, as will be shown later, does not show any 
parasitic connexion with the plants which grow in those 
places where Obolaria is generally found. 
Concerning the mestome-bundles of the leaves, these are 
rather weakly developed, and contain only a very small group 
of leptome and a somewhat larger group of hadrome. Stereo- 
matic tissue was found to be entirely absent, so that altogether 
the leaf shows a very simple structure. 
The stem of Obolaria is quadrangular, very pale, and often 
curved toward the apex. The epidermis consists of rectan- 
gular cells, with very thin, straight walls (PI. XIX, Fig. 7), 
covered with wrinkled cuticula. Stomata are present (Fig. 8), 
but they are very scarce. Only a small number of the 
epidermal cells contain anthocyan. The bark-parenchyma 
occupies the greater part of the stem-cylinder, and is com- 
posed of very thin-walled, loosely-connected cells, with very 
little chlorophyll and no deposits of starch. No stereome 
has been observed. Inside the bark-parenchyma is an endo- 
dermis (PI. XIX, Fig. 10) ; this consists of thin-walled cells, 
which show the spots named after Caspary, and forms a 
closed sheath around the mestome-bundles, of which latter 
the hadrome-element forms the most prominent part. The 
leptome is developed, not only on the exterior face of the 
hadrome (PL XIX, Figs. io and 11), but also on the interior 
face, toward the pith, and we have in this way what De Bary 
has designated as ‘ bicollateral mestome-bundles. 5 Mestome- 
bundles of this form have been observed in numerous families, 
and have been described by various authors, for instance, 
Moebius and Petersen. According to Gilg, they seem 
especially characteristic of the Gentianoideae. The exterior 
leptome is well developed, and forms an uninterrupted 
ring around the hadrome-cylinder. The interior leptome, 
on the contrary, forms merely small groups, which border 
on the inner part of the hadrome. These groups are 
