158 01. AF (, V1.I.0K 



devoid of gonidia, which is sunk into the substratum and which 

 corrodes the individual grains of mineral matter. According to A. 

 Friederich this hyphal layer is thin in the silicicolous lichens, 

 and cannot at all be compared, as regards size, with the corres- 

 ponding tissue in the calcareous lichens. Besides, according to 

 Friederich, it is never furnished with oil-hyphse or sphaeroid- 

 hyphse; but according to Bachmann, such are said to occur. At 

 any rate, Fiinfst tick's investigations show that where the same 

 lichen grows both on calcareous and on siliceous rocks, the indi- 

 viduals from the calcareous rocks contain oil, while those from the 

 siliceous rocks do not. Ftinfsttick, whose results have since been 

 strongly supported by E. Lang's renewed investigations, appears 

 to differ somewhat from Bachmann as regards the occurrence of 

 oil-hyphse in the silicicolous lichens; this disagreement need not, 

 however, be a fundamental one, as there will probably be various 

 degrees with regard to the oil-contents connected with the larger or 

 smaller amount of lime contained in the rock-species in question. 

 At any rate, it is certainly an undisputable fact that the amount of 

 oil is greatest in the calcareous lichens. 



The biological importance of the oil-contents is much contested. 

 Zukal is of opinion but quite wrongly, according to Ftinf- 

 st tick's investigations, - that the oil is a supply stored for fruit- 

 setting. Hulth also, regards the oil-containing tissue as reservoirs 

 for reserve food-material. Funfstuck shows that there exists no 

 connection between the fruit-setting and the oil-contents, and is of 

 opinion, that the oil is an excretion formed owing to the accumula- 

 tion of the carbon dioxide, which is set free by the hyphse pene- 

 trating into the calcium carbonate. 



As mentioned by Bachmann and Stall lecker the hyphae 

 affect the mineral grains in various ways. According to Stah lecker 

 they corrode quart/. This is denied by Bachmann. Basic mineral- 

 grains are affected before the acid mineral-grains, according to Stall 1- 

 ecker. When there is a decided cleavage-plane in the mineral-grains 

 (as in mica), the hyphae, according to Bachmann, follow the di- 

 rection of the cleavage, whereby the existing cleavages are widened 

 and filled with hyphae. 



The epilithic part of the thallus contains gonidia. It frequently 

 consists of a growing lichen-mycelium produced centrifugally from 

 the centre of germination, bearing on the thallus numerous small, 

 rounded or irregularly angular areas containing gonidia; according 



