STRUCTURE OV AGARICS. 11 



contents, with the cystidia, which are also bright, and found on the 

 hymenium, and at the margin of the gills. The degree of abund- 

 ance of these cells vary according to conditions which have not 

 been studied as amongst the phanerogams. One sees, in effect, 

 what enormous differences of aspect the same species, here smooth, 

 and there extremely velvety, can present. It is the same with 

 fungi, of which the hairs, scales, viscid, and soft state seldom vary 

 much. One may easily guard against confounding the scales aris- 

 ing from the debris of the volva with the productions of which we 

 have just spoken. There are also some scales which have the same 

 specific importance ; they are formed either upon the stipe or upon 

 the pileus, by a stoppage of the development of the external stra- 

 tum of cells, which, not following that of the internal parenchyma, 

 break and leave at the surface of these organs more or less irregular 

 fragments, thus causing the external suberous layers of the bark 

 to present a cracked appearance. Agaricus obturatus, Fr., often 

 presents itself under this aspect in our region. Krombholz has 

 also given a figure under the name of Agaricus obturatus rimosus. 

 The dessication caused to the periphery by external agents has 

 great influence upon this phenomenon. I have often discovered, in 

 a dry time, some Agaricus melleus, Wahl., the stipe of which pre- 

 sented some circular rings ; their origin can only be attributed to 

 the dessication of the external cellular layer, during which the 

 stipe increases in height. There are some Agarics with which the 

 elongation of the stipe is such that it is scarcely possible that ex- 

 ternal agents act in this sense, and one cannot call it a sort of 

 deformity in them. 



The agglomeration of the coloured granules to which the fungus 

 owes its colour, either in the cells disposed in phaneres, or simply 

 epidermic cells, is also subject to many variations. I cannot say 

 whether the want of colour, the albinism has been noticed in many 

 fungi, but I have in several cases encountered it upon some well 

 characterised and easily recognised species ; among others Agaricus 

 semiglobatus, Batsch. ; Agaricus coronillus, Bull ; Agaricus micans, 

 Bull. By the side of this fact there is another quite opposite, it 

 is the greater intensity of colouration, according with the bases of 

 temperature ; I have had occasion to verify it so frequently that I 

 can no longer doubt it. Agaricus nudus, Bull, is found during 

 winter in the parks in the neighbourhood of Montpellier; according 

 as the temperature falls, it takes a dark violet, almost black, or a 

 deep brown. "When the spring arrives one finds some almost white 

 individuals, shaded with lilac, or fawn colour, as we have proved 

 upon an exposed hillock at midday. Agaricus terreus, Schreff., and 

 Agaricus dryophilus, Bull, which accompany Agaricus nudus and 

 pass the cold season with it, present with it the same phenomena. 



I found, during December last, at a very cold time, in a farm 

 yard of the Chateau Levat, a well characterised Agaricus medius, 

 Schum., and the microscopic analysis has confirmed its identity, 



