DISEASES OF TAXODIUM AND LIBOCEDRUS. 55 
on their hosts and those which live for a longer or shorter 
period with their host without producing such effect.”’ * 
To the first class belong all such plants as produce imme- 
diate death, like Peronospora, Agaricus melleus and many 
Polyporei, and those producing hypertrophies, such as 
Gymnosporangium, Exoascus, and others. To the second 
class belongmany Uredineae and Ustilagineae, Exobasidium, 
ete. In the latter cases the mycelium may live for a long 
period in the cells without any perceptible effect on them. 
The reason for this ‘ conservation ’’ (Tubeuf, 1. ¢.) is 
doubtless to be sought in complex chemical conditions which 
bring about one kind of effect with one, and another with a 
different fungus. 
In all the cases just mentioned, one is dealing with living 
tissues capable of reaction of some sort. This reaction 
may take the form of starch accumulation, hypertrophied 
structures or the formation of products antagonistic to the 
growth of the invading fungus. The bacteria are a good 
example of organisms bringing about the last form of reac- 
tion, i. e., where the host produces substances which 
neutralize the poisonous products formed by the parasite. 
To what extent similar processes take place in plant cells is 
yet unknown, but there seems to be no reason why they 
should not. 
In the heartwood of a tree one is dealing with a plant 
member to all intents and purposes dead, i. e., its power to 
react to any stimulus has been lost, so that such influences 
as would affect the distribution as well as chemical activi- 
ties of a mycelium in a living member can have no bearing 
here. There isin the Taxodium a marked localization, 
and, as will be shown, this is also present in Libocedrus 
decurrens, Juniperus Virginiana, J. Bermudiensis, and to 
some extent in pines attacked by several of the Polyporei. 
The localization of chemical action, for such the disinte- 
* Tubeuf, C. Freiherr von. Diseases of plants 21. 
33 
