TREE-KILLING FUNGI. 389 



cells far beyond their immediate neighbourhood, extracting from them certain 

 matters which serve for the nourishment of the fungus-hyphoe, whereby the most 

 extraordinary differences, characteristic for each species of plant, appear. In many 

 cases the wall of the wood-cells again assumes completely the character of cellulose : 

 it becomes colourless, flexible, capable of swelling, and is coloured a beautiful violet 

 by chlor-zinc iodine. In other cases, on the other hand, the wood cell-wall becomes 

 brown and very brittle, its substance largely soluble in ammonia, and yielding a 

 brown fluid W'ith solution of potash. This, in other words, evidently means that 

 some of these Fungi take up chiefly wood-substance (xylogen) from the cell-wall 

 and leave their cellulose behind, while others take up the cellulose itself, and leave 

 behind the wood-substance impregnating it. The former is the case for example 

 with Trametes pmi, and the latter with Polyporus mollis. Hartig is of opinion that 

 the greater part of the organic substance of the wood finally breaks up into 

 carbon dioxide and water, without being previously taken up into the hyphae. In 

 very much decomposed wood of Conifers the turpentine appears no longer fluid 

 but hardened, filling the cavities of the wood-cells in amorphous pieces. In the 

 wood of Pines much decomposed by Trametes radicipcrda, the tracheVdes, previously 

 permeated with turpentine, become filled with crystals, the solubility of w-hich in 

 turpentine admits of the conclusion that they are hydrate of terpin. Obviously 

 the mycelia of the tree-killing Fungi take up their ash-constituents also from the 

 wood, and these pass into the fruit bodies situated on the exterior. As in the case of 

 most other Fungi, crystals of calcium oxalate are here also excreted during nutrition, 

 both in the nourishing wood and in the organs which bear fructification. 



If we now cast another glance backwards on what has been said concerning 

 the nutrition of Fungi, we find forms which are satisfied with taking up from their 

 living or dead substrata simply and only so much of what is needed for the construc- 

 tion of their bodies as is necessary; as well as those which, in addition to absorbing 

 their nourishment, produce copious decompositions in the substratum and destroy it. 

 This latter effect, which, as it seems, occurs in the most various degrees down to those 

 which are scarcely noticeable, we may comprehend in general — even in cases where 

 the decomposition of wood is concerned — under the extended idea of fermentation. 

 With respect to the true na'ture of fermentation, and especially with respect to its 

 essential difference from ferment-actions, I have already said what is necessary 

 (Lecture XXI). Here it may be still further insisted upon that neither action need 

 exclude the other. In the first place, we must assume that every Fungus exerts a 

 ferment-action on its substratum, simply in order to obtain its nutritive material from 

 it. When a fungus-filament grows through a hard cell-wall, we must assume that a 

 ferment exists at its surface, by means of which not only is cellulose dissolved, but 

 also lignine, and, imder certain circumstances, cuticular substance also. In the same 

 way the germinal hyphae of various parasitic Fungi bore through the coverings of the 

 bodies of insects, for which purpose (in the same way, and probably necessarily) a 

 ferment must exist at the surface of the germinal hypha, which in this case, where 

 the solution of proteid substances and perhaps even of chitin is concerned, may be 

 regarded as apeptonising ferment. In general it will suffice that the fungus- filament 

 which penetrates into a substratum contains an exceedingly small quantity of 

 ferment, since even in the seedlings and buds of Phanerogams only extremely small 



