BACTERIA. FUNGI. 167 
wood is destitute of tannin. It is natural to suppose, therefore, that the mycelium 
takes away and uses up the tannin. It has also been observed that wherever the 
hyphe of the Pine-blister (Peridermiwm Pint) ensconce themselves, the nitrogenous 
parts of the protoplasm and the starch vanish, whilst turpentine remains behind, 
clinging in drops to the inner walls of the cells. These are, to be sure, very sparse 
data; but they show that the entire cell-contents are not absorbed by the parasite 
unaltered, or used in that condition as material for the building up of its own body. 
Not only the contents of the cells preyed upon, but the walls as well, are partially 
used as food by the hyphz which penetrate into the woody axes of arborescent 
angiosperms and gymnosperms. The mycelium of several species of Polyporus and 
Trametes begins by bringing the lignin in the cell-walls into solution, leaving 
nothing but a pale-coloured cellulose wall. Soon afterwards, the so-called middle 
lamella, which connects adjoining wood-cells, is also dissolved, and the colourless 
wood-cells, now almost like asbestos-fibres in appearance, fall apart at the slightest 
touch. When the wood of a larch has been infested by the mycelium of Polyporus 
sulfwreus, there are always deep furrows running obliquely on the internal walls of 
the wood-cells; this loss of substance, too, can only arise from the solution, and 
absorption as nutriment, of parts of the walls by the action of the hyph«. 
All decompositions and alterations of structure of the above kind within the 
precincts of the host’s cells are naturally followed by a disturbance of function, and 
ultimately by death. The entire plant is, however, but rarely killed by parasites 
belonging to this group. The decomposition by bacteria of a mammal’s blood, 
though at first confined to a particular part of the body, spreads in a moment 
throughout the whole organism, owing to the heart’s action and the circulation of 
the blood. But the decomposition taking place in the manner just described, 
through the intervention of hyphze, propagates itself, on the contrary, only very 
gradually from the cells immediately attacked to their neighbours, and it gets 
weaker and weaker as the distance from the site of the invasion increases, a 
circumstance to which we shall recur later on when discussing the phenomena of 
fermentation and decay. The nature of the parasite and the power of resistance of 
the host have an undoubted influence on the rate of distribution. In many cases 
alteration is limited to the cells attacked and those immediately adjoining, so that 
the area destroyed is circumscribed. It is manifested on fresh green leaves, often 
merely in the form of small, isolated, yellow, brown, or black spots and patches, 
which only slightly interfere with the activity of the leaf, and do not cause it to 
change colour, wither, or fall off any earlier. In other instances, however, the 
entire leaves and stem do undoubtedly become flaccid and shrivelled and dried up 
into a black mass, looking as though they had been carbonized; or else putrefaction, 
such as that which is excited by bacteria, invades the whole mass. 
As above stated, when the wood in the trunks of trees is perforated and 
consumed by hyphe it is resolved into fragments. It becomes rotten, takes the 
form of an asbestos-like or crumbling and pulverulent mass, and is then obviously 
no longer capable of fulfilling its various functions in the living plant. If the 
