CHAPTER I. — HISTOLOGICAL CHARACTERISTICS. 15 



green colour of the decaying wood must be a consequence, and the colouring matter 

 a product of the Peziza which grows in and upon it. The question is still undecided ; 

 but I have myself recently observed the important fact, that green-rotted wood is 

 sometimes found in which microscopic examination can discover no evident colora- 

 tion of the wood elements, but shows the presence inside them of numerous in- 

 tensely green hyphae which most certainly belong to Peziza aeruginosa. All our 

 observations show that the Fungus wherever it occurs always contains the green 

 colouring matter ; it occurs only in green-rotting wood, and the view that the wood 

 owes its colour to the Fungus must be allowed to be probable. The fact that wood 

 is found with this particular form of decay but unquestionably free from the Fungus 

 appears to be quite irreconcilable with this view ; but the objection disappears if 

 we suppose with Cornu that the hyphae of the Peziza which vegetate in the wood are 

 short-lived, and convey all their colouring matter to the wood when they die. It 

 ought not to be difficult to settle this question by artificial cultivation. 



One striking case of coloration may be added here, though strictly speaking it does 

 not belong to our present subject. The tissue of the pileus of certain Boleti, especially 

 Boletus luridus which in the uninjured state is yellow, assumes a blue colour as 

 soon as it comes into contact with the outer air. Schonbein has carefully examined 

 this phenomenon, and finds that it is a substance capable of being extracted from the 

 Fungus by alcohol and probably of a resinous character which turns blue in the 

 air. The blue colour appears in the alcoholic solution under the same conditions 

 as it does in a- solution of guaiac-resin, and since it has been proved that the 

 colour is produced in the latter by combination with ozonised oxygen, Schonbein 

 assumes a similar cause of the blue colour in the Fungus. The alcoholic extract 

 from the Boletus does not by itself become blue when exposed to the air ; there 

 must therefore be another substance contained in the Fungus, which ozonises 

 the oxygen of the atmosphere, and then effects a combination with the resin, 

 giving off the oxygen to it in the state of ozone. Phenomena of a similar kind 

 observed in other cases confirm this conjecture. Thus both the tincture of guaiac 

 and the alcoholic extract of Boletus turn blue at once, if they are allowed to fall in 

 drops on the fresh tissue of some of the Agarici which do not themselves turn blue, 

 especially Agaricus sanguineus. The watery juice of Agaricus sanguineus squeezed 

 out from the plant and filtered produces the blue colour at once in both tinctures. 

 From these facts it may be concluded that a number of fleshy Fungi contain a 

 substance soluble in water, which absorbs oxygen and gives it up to other bodies 

 in the state of ozone. The Boleti which turn blue contain this substance with 

 another resinous substance, which like guaiac-resin is turned blue by ozone. 



Literature of sections II and III :— 



i. Cell-structure of the Fungi ; structure and chemical composition of the cell- 

 walls. 



Schacht, Die Pflanzenzelle, p. 136 ;— Id. Lehrbuch d. Anat. d. Pfl. 



Coemans, Monogr. du genre Pilobolus in Mem. des savants Strang. Acad. Bruxelles, 



XXX. 

 Caspary, Monatsber. d. Berliner Acad. Mai, 1855. 

 H. Hoffmann in Bot. Ztg. 1856, p. 158. 

 H. v. Mohl in Bot. Ztg. 1854, p. 771. 

 De Bary, Unters. fiber d. Brandpilze ; — Id. Ueber Anthina in Hedwigia, I. 36 ; — 



Id. in Bot. Ztg. 1854, p. 466. 

 BRACCONOT in Ann. de Chimie, XII. 172. 

 Payen, Memoire sur le developpement des vdgetaux in Memoires presentes a l'Acad. 



des sc. de France, IX (1846), p. 21. 

 Mulder, Physiol. Chemie, Braunschw. 1844-51, pp. 202, 203, where Fromberg's 



results are also given. 



