,G\- TAIKY RINGS. .^{J9 



r Had Df. Withering frequently repeated this examination Spawn of fungi 

 of the soil he would have corrected the last remark, which found' mXr 

 is not universally true, as the grass may at some period be th e luxuriant 

 found luxuriant even over the undecayed spawn. During grass * 

 the growth of the fungi, they so entirely absorb all nutri- 

 ment from the soil beneath, that the herbage is for a while 

 destroyed, and a ring appears bare of grass surrounding 

 the dark ring. If a transverse section be made of the soil 

 beneath the ring at this time, the part beneath the fungi 

 appears paler than the soil on either side of it, but that 

 which is beneath the interior circle of dark grass is found 

 on the contrary, to be considerably darker than the ge- 

 neral surrounding soil. But in the course of a few weeks 

 after the fungi have ceased to appear, the soil where they 

 stood grows darker, and the grass soon vegetates again 

 with peculiar vigour; so that I have seen the surface co- 

 vered with dark grass, although the darkened soil has n«t - 

 exceeded half an inch in thickness, while that beneath has . 



continued white with spawn for about two inches in depth. 



The section of the space occupied by the white spawn has Progressive. 

 in general nearly the same form, and may be compared to course of the 

 that of a wave proceeding from the centre outwards, as. its 

 boundary on the inner side ascends obliquely toward the 

 surface, while its exterior termination is nearly in a ver- 

 tical position. The extent occupied by the spawn varies 

 considerably according to the season of the year, being 

 greatest after the fungi have come to perfection, and is re- 

 duced to its smallest dimensions, and may in some cases 

 not be discernible, before the next year's crop begins to make 

 its appearance. 



For the purpose of observing the progress of various Annua! in- 



circles I marked them three or four years in succession, by crea , se ° - 



J i J circle various. 



incisions of different forms, by which I could distinguish 



clearly the successive annual increase, and -I found it to 



vary in different circles from eight inches to as much as two 



feet. The broadest rings that I have seen were those of Br °a de st when 

 ., , " \ . . from the com- 



the common mushroom (ag. campestris); the narrowest mon mus h- 



are the most frequent, and are those of the champignon roo,n : " ar " , 



J* ' r ■ rowest from th ". 



(ag. oreades of Dr. Withering). Ihe mushroom accord- champignon. 



iugly makes circles of largest diameter, but those of the 



\ ol, XIX. — Supplement. B b champignon 



