of some Phanerogamic Parasites. 31 1 
cells of the host which surround them, and carrying with them 
for a short distance the compressed cortical and epidermal 
cells which immediately overlaid them in the mother-plant. 
The sucking-cells at their tips, springing all of them from the 
shafts, penetrate the cells into contact with which they come 
by the same processes as previously described. I have been 
unable to find in the hosts, beyond the first few layers, any 
cells which come from the ordinary cortex of the parasite. 
The young haustorium does push some cortical cells into the 
host, but only for a very short distance. These are elongated 
by the pressure ; they do not grow in as one might infer from 
their shape ; they are pushed in, and do not long survive; they 
form part of the sheet of compacted cell-wall which enwraps 
the haustorium on its entrance into the host. We must return 
to the older idea of Mohl 1 , cited by Koch, that these haustoria 
are roots only, not thalloid structures to which several tissues 
contribute, as Graf zu Solms-Laubach 2 , with whom Koch 
agrees, is led to believe by his studies on other haustoria. 
As already shown by L. Koch, a well-developed haustorium 
imbedded at its distal end in the tissues of a host consists of 
a central strand of tracheids, the rather thick walls of which 
are marked with large deep pits or coarse reticulations. I have 
seen no spiral or annular markings. Their absence seems to 
add some confirmation to the theory that they are formed 
only in cells which must be strengthened in a way which will 
not interfere with their elongation. Since the haustorium, 
like all roots, grows only at its tip, manifestly no such provision 
is necessary ; and the greater lightness of the spiral or annular 
thickenings is not a desideratum since the structure does not 
have to maintain even its own weight, but is imbedded. 
This strand of tracheids, united at the base of the haustorium 
by two lines of tracheids developed in the interfascicular 
parenchyma, with the xylem of generally two bundles in the 
1 H. v. Mohl, Ueber den Bau u. das Winden der Ranken u. Schlingpflanzen. 
Tubingen, 1827. 
2 Graf zu Solms-Laubach, Das Haustorium der Loranthaceen, Abh. d. nat. Ges. 
zu Halle, Bd. XIII, Heft 3. 
