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 

 hyphae 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- 

 aclilya perforans, and determined them in the Silurian coral 

 Goniophyllum pyramidale, the Devonian coral Calceola san- 

 dalina; also in a Silurian Cyathophyllum 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. T. State Museum Bui. 39, p. 223. 1900. 

 sSitzungsb. d. k. Akad. d. Wissensch. v. 33, p. 451, pi. 1-3. 1858. 

 *Quar. Jour. Geolog. Soc. London, v. 32, p. 205, plate. 1876. 



s"Sur les algues perf orantes, " Bui. Soc. Botanique de France, v. 36, 

 p. 147. 1889. 



