of some Phanerogamic Parasites . 297 
(see Fig. 8) consist of a stem in which, instead of a regular 
ring of scattered bundles uniform in size, the ring be wavy, 
with large bundles on the crests and single small bundles 
in the rather deep depressions of the ring, the haustorium, 
having applied itself laterally to one or two bundles of 
adjacent crests and continuing to grow toward the centre 
of the host, will come directly upon the smaller bundle in 
the depression. Instead of dissolving its way into and 
through this bundle, the tip divides into two parts which 
pass on opposite sides of the bundle, with which they both 
presently unite. In other words, the fibro-vascular bundle 
in the depression of the general ring divides the haustorium 
like a wedge, and the haustorium, instead of uniting with 
one or two, unites with three fibro-vascular bundles and 
destroys none. The advantage to the parasite of this arrange- 
ment is evident. Such is the case of the undetermined 
Apocynaceous host in Dr. Johow’s collection, as shown by 
Fig. 8. 
The other species of Mimoseae and Thevetia neriifolia show 
still a third mode of growth. In these the fibro-vascular 
bundles soon become confluent, first in their xylem area, later 
in the soft bast. The hard bast masses in Thevetia remain 
distinct. In the Mimosa a sclerenchyma-ring takes the place 
of the hard bast. As the haustorium grows into these plants, 
it meets in the Mimosa , and may meet in Thevetia , a strongly 
lignified mass of thick-walled cells. These, however, resist 
the solvent action of the haustorial cells only for a short time, 
and the sucker applies itself to the ring of soft bast. This it 
more quickly penetrates, and finally attacks the wood-elements 
which in both hosts are closely compacted, thick-walled, and 
thoroughly lignified. These it dissolves much more slowly 
and, depending upon the age and thickness of the wood, more 
or less completely (see Fig. 9). It is seldom that the haus- 
torium reaches the pith in the Mimosa ; it does sometimes in 
Thevetia . The parasites, in uniting with the conducting tissues 
of these two hosts, do so by destroying part of the conducting 
tissues. The vitality of the hosts is thereby considerably 
