1905.] on Fungi. 25 



organ of a plant, bored its way in, or through a stoma, and entered 

 the tissues. Here it lives, as does a plant in any other medium, at the 

 expense of the substances in the tissues, which it eventually kills. 

 It then emerges and develops its spore on the outside. 



Thus was founded the " germ theory" of disease. 



The lecturer here gave illustrations of the kinds of parasites 

 refeiTed to, and showed how the spotting of leaves is brought about 

 by various epiphytic and endophytic forms, such as Oidium and 

 Erysiphe, Phytophthora, Ustilaginte and Uredina3, etc., and directed 

 attention to certain special genera, such as Botrytis, Aspergillus, etc. 



That the ancients were acquainted with the phenomena of rot in 

 timber is attested by remarks of Theophrastus on hollow trees and the 

 decay of oak ; but it was not until about 18:30 that any idea of con- 

 necting the phenomena with fungi can be traced, and even then 

 Theod. Hartig who discovered hyphse in the rotten wood, thought 

 they originated from the wood-fibres themselves. Schacht. in 1850 

 and 1868, figured many instances of hyphae in wood, and showed that 

 the fungus fed on the starch, pierced the cell- walls, and in some way 

 induced their putrefaction ; and to these and Willkomm's researches, 

 in 1864, we may trace the origin of our knowledge of fungi as the 

 causes of decay in timber. 



Meanwhile the palaeontologists also were bringing forward examples 

 of fungus-hyph^ in fossil woods. 



But the real founder of this important subject was R. Hartig, who 

 in his works, 1874 and 1878, proved that not only are there several 

 kinds of wood-rots in different species of trees, each induced by 

 different forms of fungi, but that the different Avoods show special 

 markings, and break up in a peculiar manner for each case, so that par- 

 ticular kinds of rot can be recognised by particular symptoms. 

 Hartig, moreover, showed how the fungi got into the tree, and that 

 these wound-fungi have special peculiarities of their own. He traced 

 their hyphae into the vessels and wood-elements, showed how they 

 pierce the cell-walls, and, most important of all, proved that they 

 dissolved out from the wood-elements the lignified constituents to 

 which their fundamental physical properties — as wood — are due, and 

 either leave the delignified walls soft and cellulose in character or 

 dissolve them to a jelly. 



Here the lecturer showed illustrations of the mode of action of 

 dry rot, of Polyporus igniarius^ and of other wood-destroying fungi, 

 and referred to Czapeck's recent discovery of Hadromal, the probable 

 uniform constituent of wood hitherto vaguely known as Lignin. 



In another direction attention was turned to the fungi which attack 

 insects, and which are now known often to become epidemic, to the 

 great advantage of areas devastated by locusts, cockchafers and other 

 grubs, caterpillars, etc. 



It is a remarkable fact that, whereas the diseases of plants due to 

 fungi are numbered by their thousands, only some two hundred or so 



