CHAPTER VII. PHENOMENA OF VEGETATION. GENERAL CONDITIONS. 355 



ment of some Basidiomycetes '. Shades of difference varying from one species to 

 another are found within these average limits. 



Respect must also be had to certain physical conditions in the food-material as 

 well as to its chemical qualities. This was shown by the fact that the plants thrive 

 differently according to the difference in concentration of the same good nutrient 

 solutions 2 . Dependence on other things, such as cohesion and conditions of 

 imbibition, may also require to be taken into account in many cases, especially among 

 parasitic Fungi. 



It follows of course from universal physiological laws that a process of respiration 

 accompanies that of nutrition in the vegetating Fungus-cell, as free exhalation of 

 oxygen or as intramolecular respiration. 



Since Fungi take up food-material from the substratum, and cause fermentations 

 or more or less perfect combustion of the substratum by their processes of respiration, 

 they must necessarily produce chemical changes in the organic bodies in which they 

 live; they also give rise in numerous cases to unorganised ferments with specific 

 modes of operation. Species of Saccharomyces, Penicillium, and Aspergillus niger 

 not however Mucorini which excite alcoholic fermentation in a solution of grape- 

 sugar 3 produce invertin which splits cane-sugar into dextrose and laevulose. 

 The mycelial hyphae of many Fungi and the germ-tubes of many parasites 

 on other plants grow in thick even lignified or cuticularised cellulose-membranes 

 and in starch-granules, and make passages through the parts which may cause, 

 as Hartig has so well shown 4 , wide-spread destruction in the woody tissue. 

 The lignin first of all in the walls of the tracheides in pine-wood, then the 

 cellulose, and finally the middle lamella is dissolved according to Hartig by Trametes 

 radiciperda and T. Pini. Similar effects are produced by other wood-destroying 

 Hymenomycetes. The hyphae of Cordyceps spread widely in the thick chitinous 

 investment of the larvae of insects. These facts distinctly prove the secretion of 

 solvents, and we can scarcely conceive of these in any other form than that of 

 ferments. 



We have become' acquainted during the last twenty or thirty years with a very 

 large and varied series of phenomena connected with Fungi and their substrata and 

 with a corresponding number of specific adaptations between them. It will be 

 necessary now to take a somewhat closer view of these adaptations and therefore of the 

 habits of the Fungi as they have been observed and their effects on the bodies which 

 they inhabit. With respect to special chemical questions the reader is referred to 

 treatises on the chemistry of fermentation, and to pathological works for some 

 questions which arise on the subject of the aetiology of diseases. 



1 Brefeld, Schimmelpilze, IV, p. 7. 



* See especially Raulin, as cited on last page. 



3 See Pfeffer, Phys. I, 282. Bechamp, in Comptes rendus, 36 (1833), p. 44. Gayon in Comptes 

 rendus, 86, p. 52. 



4 Hartig, Die Zersetzungserscheinungen d. Holzes, Berlin, 1878, and Lehrb. d. Baumkrankheiten, 

 p. 78. Among the earlier literature may be cited : Unger in Bot. Ztg. 1847. Wiesner, in Sitzgsber. 

 d. Wiener Acad. Bd. 49. Schacht, in Monatsber. d. Berl. Acad. 1854, and Lehrb. d. Anat. I, 160, 

 and in Pringsheim's Tahrb. Ill, 442, &c. 



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