S'l s l)DY OF PATHOLOGY. M 



of the leaves ; but there was invariably only one on each 

 leaf. When the leaves, or at least a great part of them, 

 were yellow, then the brownish patches so apparent on the 

 green leaves were no longer to be seen, but instead thereof 

 the whole leaf had taken on a similar colour, from which 

 it follows that the disease in question, in a longer or 

 shorter time, causes the whole leaf to wither and to die. 

 The occasion of the appearance of the disease rests, in any 

 case, on insufficient nourishment bringing about a dis- 

 turbance in the vegetation, in which a rupture in the 

 cuticle and the adjacent cell walls takes place. These 

 latter are then also killed, and are absorbed in the exten- 

 sion of the brownish patches, and are intensely browned, 

 while simultaneously with the rupture of the epidermis 

 there occurs a great effusion of resin, which fills to the top 

 the aforementioned furrows. But from this it follows that 

 the origin of any disease appearing in connection with this 

 fungus, does not lie in it, or in any other parasite, but 

 must be considered a pathological incident. The Conio- 

 thecum must also be considered as only a pseudo-parasite, 

 which does not induce any injurious change on the tree ; 

 but which from the first settles down upon the resinous 

 secretion from a wound, when any such has been produced 

 by some foreign influence; and which also, when it has 

 taken possession of the whole surface of this, does not pass 

 on to the portion of the leaf surrounding it, but satisfies 

 itself exclusively with drawing its nutriment from the 

 resin : never is any trace of mycelium to be found in the 

 leaf. As, moreover, experiments in endeavours to infect 

 leaves with it yield nothing but a negative result, we may 

 with assurance advance the conclusion that whatever 

 appearances to the contrary may present themselves, 

 Coniothecum Austriaca is not a fungus injurious to forests. 



' We have, in this brief resume considered only the 

 more injurious parasites, and this newly-discovered species 

 Coniothecum Austriaca] all others being considered as Sap- 

 rophytes, up to the present time at least, we have passed 



