22 DR. J. H. GILBERT ON THE 



association with them ; or, lastly, have these plants the power of 

 assimilating nitrogen in some form from the atmosphere, or in 

 some form or condition of distribution within the soil not avail- 

 able (at least when in competition) to the plants growing in asso- 

 ciation with them ? 



It is with the hope of arriving at some answer to these ques- 

 tions, either from the existing knowledge or the future obser- 

 vation of botanists and vegetable-physiologists, that we have 

 felt it desirable to comply with the request made to us, to bring 

 our own observations, made from a special point of view, before 

 the Fellows of the Linnean Society. In aid of this object it may 

 be well to state some other facts which we have noticed in con- 

 nexion with the formation and extension of " fairy-rings." 



It is probable that the fungi growing on meadow-land owe their 



dropp 



specimens 



animals or birds. Individual 



grow to a large size, even on some of the highly manured plots ; 

 but patches, or " rings," are chiefly found on the poorly manured or 

 exhausted plots— that is to say, where there is a marked absence 

 of luxuriance in the vegetation generally. So far as may be 

 j udged from observation hitherto, patches may form and die out 

 without development and extension into " rings." The formation 

 of an annually increasing "ring" seems to require special condi- 

 tions, both as to soil and association. In the case of mere 

 patches, some examinations of the soil in spring and autumn have 

 not shown a marked development of mycelium where it would be 

 expected if there were to be extension, though it would appear 

 that, if the conditions be specially favourable, they may enlarge 

 and endure for some time. In the case of extending " rings," on 

 the other hand, the soil under the outer portion of the circle gene- 

 rally shows, to a depth of a foot or more, according the character 

 of the soil, an enormous development of mycelium for some time 

 prior to the appearance of the above-ground growth. 



It is to be particularly observed that this development of myce- 

 lium is always under the outer portion of the " ring," and is not 

 found within it. When a ring is formed, what happens seems 

 to be the following :— From some extraneous cause, such as above 

 referred to, a patch of fungi is established. The plants falling 

 and dying supply a rich nitrogenous (as well as mineral) manuring 

 to the adjacent herbage. A patch of dark green luxuriant grass, 

 generally several inches higher than the surrounding herbage, 





