ORGANIC DEPENDENCE AND DISEASE 
81 
cavities made by certain sea urchins are not included in the 
present category. 
Plants. Our attention may be given first to the plant 
parasites of the Paleozoic rocks. These are invariably very 
minute filamentous tubes often showing the swellings of 
liyphae or sporangia. There has been a constant and con- 
tinuing difference of opinion among the students of the liv- 
ing forms of such boring plants, as to whether these are to 
be regarded as fungi or algae. Kolliker 1 believed them all 
to be fungi, as he could not satisfy himself that the fila- 
ments in the living forms showed cell partition. Loomis 2 
has also identified as fungi such occurrences in the Clinton 
(Silurian) fauna of New York; while Wedl regarded the 
living forms as algae 3 and Duncan , 4 who specially studied 
these borings in fossil corals of the Silurian, Devonian and 
Tertiary, agreed in regarding these minute tubules the 
work of unicellular algae. Naturally the distinction in the 
fungous and algal character of these borings in the fossil 
state is very difficult, and for our present purpose not of 
high importance. Duncan gave a common name to all these 
coral-boring plants regardless of geological age; Palae- 
achlya perforans, and determined them in the Silurian coral 
Goniophyllum pyramid 'ale , the Devonian coral Calceola san- 
dalina; also in a Silurian Cvathophyllum and an Ordovician 
“Foraminifer from Canada,” whatever this last may have 
been. 
The clearest light upon the nature of these boring plants 
has been given by the botanists Bornet and Flahaut 5 after 
exquisite operations in the isolation of the plants from their 
stony matrix. These investigators were able to determine 
from growth-habit, structure, sporangia and fruit, that the 
1 Op. cit. 
2 F. B. Loomis. N. Y. State Museum Bui. 39, p. 223. 1900. 
s Sitzungsb. d. k. Akad. d. Wissensch. v. 33, p. 451, pi. 1-3. 1858. 
4 Quar. Jour. Geolog. Soc. London, v. 32, p. 205, plate. 1876. 
5“Sur les algues perforantes, ’ ’ Bid. Soc. Botanique de France, v. 36, 
p. 147. 1889. 
