ESCULENT FUNGI. 



329 



other side. These rings are formed by various 

 species of mushrooms, and also by some of the 

 lycoperdons, or puff-balls ; but the cause of the 

 circular formation has not been satisfactorily ex- 

 plained. It would seem that the ground which has 

 produced one crop of fungi is not immediately fit 

 for the production of another, and thus the annual 

 sowing is outwards. It also appears that the de- 

 cayed matter of the fungi is favourable to the grass by 

 which it is succeeded. 



Black and White Truffles. 



The TRUFFLE Tuber cibarium is found grow- 

 ing in clusters some inches under the surface of the 

 ground, in a soil which is composed of clay and 

 sand. It is nearly spherical, and without any vi- 

 sible root ; of a dark colour, approaching to black, 

 and studded over with pyramidal tubercles. The 

 internal part is firm, and grained with serpentine 

 lines ; its colour is white when young, but becomes 

 black from age. Naturalists, who have examined its 

 structure with microscopic attention, affirm that mi- 

 nute oval capsules, each containing from three to 

 four seeds, are embedded in its substance. Truffles 

 are natives of the woods both of Scotland and 

 England ; but they are not produced in the same 



VOL. xv. 28* 



