113 
1 said above that haustoria are very frequently found attached 
to the roots of Gerardia itself. Such haustoria have either the shape 
of those already described (Figs. 1-4), or they are mere cylindrical 
branches growing at right angles from some Gerardia rootlet into 
another contiguous one. But, instead of single threads of vascular 
cells as described above, all these haustoria have solid, massive cylin- 
ders of vessels connecting the root fro7H which, with the root on\\W\c\\ 
they grow. In these haustoria I could not detect the remarkable 
tendency of the apical tissues to meet the descending sap-current of 
the foster-plant, the vessels are generally inserted at right angles with 
the wood cylinder of the Gerardia root. 
In some Gerardia rootlets infested with haustoria I found the 
vessels m the immediate vicinity of the haustorium apex filled with 
those hernioid protrusions which were observed by some histologists* 
growing in vessels surrounded by very active cells. The walls of 
these active cells will bulge out through the pits of a vessel into its 
cavity; then they will grow considerably, forming globular cells, and 
will eventually close up the vessel entirely. In the sections that I 
have examined the walls of these hernioid cells seem to be lignified; 
at least, they appear of the same color as the vessels enclosing them 
after staining the sections with alum carmine and aniline green. 
If I had found these " puzzling "f hernioid protrusions near all, 
01" at least near very many of the haustoria examined, I should not 
hesitate to consider them as a contrivance to defend the Gerardia 
against the senseless depredations of its own haustoria. 
I abstain, for the present, from drawing the conclusions in refer- 
ence to the nature of parasitism in general, which are most forcibly 
suggested by the above premises. J Besides, if these observations 
should prove correct, they might contribute, to a certain extent, to 
the solution of another much discussed, and still undecided,§ physio- 
ogical question — the question about the functions which the trachcary 
tissues perform in the transmission of the various fluids necessary to 
the life of plants. 
We have seen that in the parasites examined thus far the channels 
or cavities of the vessels are in close, open connection with the cell- 
cavities of the foster- root. Shall we still assume that it is only air 
which passes within these united channels? And must we still sup- 
pose that the water in plants travels within the substance of the walls 
of these vessels, and not within their cavities ? 
Hoboken, August, 1884. 
*DeBary. Vergleichende Anatomie, p. 594 ("Thyllen'O; J. C.Arthur in Ch. 
^. Bessey, Botany, p. 30. 
fBessey, 1, c. 
e only water and mineral substances from their foster-plants. 
,^ Haberlandt, Physiologische Pflan/enanatomie {18S4), p. 209: "The physi- 
ological nature of the vessels and tracheids has been discussed very frequently; stdl 
^n»s question has not yet been definitively solved." 
