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” 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 *—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‘, 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. 
2 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 Jahrb. III, 442, &c. 
Aa2 
