138 



About three inches across when fresh, extremely polymorphous ; 

 pilei at first minutely tomentose, at length quite smooth, often 

 much imbricated, with the margin inilexed and split ; stem some- 

 times quite obsolete, sometimes distinct, -^-f inch high, ^ inch 

 thick, pallid like the pilaus ; aculei ^ inch long, acute and slender, 

 somewhat decurrent when the stem is present. Not so common as 

 the last. 



It is curious that the Russvla is not considered esculent, though 

 an esteemed culinary species in Europe. 



FAIRY RINGS. 



In a recent communication to the Linnean Society Dr. J. H. 

 Gilbert draws attention to the fact that, according to published 

 analyses of various fungi, generally from one-fourth to one-third 

 of their dry substance consists of nitrogenous matters. In fact, 

 fungi would appear to be among the most highly nitrogenous of 

 plants, and to be also very rich in potass. Yet the fungi have 

 developed in " fairy rings " only on the plots poorest in nitrogen 

 and potass in such conditions as to be available to most other 

 plants. They flourish strikingly on two plots only, in neither 

 of which either nitrogen or potass is applied as manure, on which 

 the development of grasses is extremely restricted, and their 

 limited growth is due to a deficient available supply of nitrogen, 

 or of potass, or of both, and, where the completion of the Legu- 

 miuosae is also weak, in the absence of a more liberal supply of 

 potass. 



The questions obviously arise whether the greater prevalence of 

 fungi under such conditions be due to the manurial conditions 

 themselves being directly favourable for their growth, or whether 

 other plants — especially grasses — growing so sluggishly under 

 such conditions, the plants of the lower orders are the better able 

 to overcome the competition and to assert themselves. On this 

 point the further questions arise, whether the fungi prevail simply 

 in virtue of the absence of adverse and vigorous competition, or 

 whether to a greater or less extent as parasites, and so at the 

 expense of the sluggish underground growth of the plants in 

 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 available 

 (at least when in competition) to the plants growing in association 

 with them. 



