386 BOTANICAL GAZETTE [MAY 
by the presence of the fungus. The leaves are attacked in the bud 
and very soon after their emergence (DuGGAR 18). Cytologic 
changes may also occur when the fungus acts slowly for any reason. 
If the fungus is a weak parasite or if the host is not the best suited 
to the fungus, the host will have time to react to the fungus, and 
- notable changes may be expected, both in the cell and in the tissue 
as a whole. That there is a difference in the speed with which 
various parasites work is seen from the fact that some diseased 
tissues show cells in various degrees of degeneration or death, while 
in others there is no intergrading condition between the dead, 
brown cells of the diseased area and the normal cells of the healthy 
tissue. The Gaylussacia described above shows relatively slow 
action of the parasite, as is proven by the two following conditions. 
First, the cells react by showing a granular protoplasm, then a 
uniform mass of broken-down protoplasm, which is stained brown, 
and finally nearly empty cell walls. It is improbable that this 
gradual degeneration is merely a process that would normally 
take place in cells which are breaking down, because often, as in 
Castanea, none of these intergrading forms are found. Second, 
it is to be noted that in Gaylussacia, and other hosts reacting 
similarly, the cuticle and the epidermal cells are often affected 
before the mesophyll, as the fungus spreads from the center of 
infection. This tends also to prove that the fungus acts progres- 
sively and slowly enough to be observed in the successive steps. 
Psedera, Viola, and Panicum act somewhat similarly in that they 
show changes in the size and number of nuclei, etc., as cytologic 
changes induced by the slow action of the respective parasitic 
fungi. It should be noted in passing, also, that in the case of the 
rust which was parasitized with Darluca, there was a different 
effect produced upon the nuclei of the leaf cells from that produced 
by the unparasitized rust. In the latter case the nuclei seem to 
have disappeared, while in the former case the nuclei are present 
but very abnormal (fig. 4). It is perhaps significant that nuclei 
were found only in places where the rust was parasitized, and 
presumably lowered in its vitality. If the latter statement is true, 
then the rust would not be able to act so quickly as normally, 
thus giving the host time to react to its influence. 
