38 Ward . — Recent Researches on the Parasitism of Fungi . 
As regards the crossed Wheat C, one or two incipient pustules only 
could be detected on the tenth day, and on the twelfth it was as badly 
infested as the susceptible form, the numbers of spore-bearing pustules 
being far too many to count. 
We then fixed the infected areas of leaves of each at intervals on 
the third, fourth, fifth to the eleventh days respectively, cut, stained, &c., 
and examined the serial sections. Several of each were left growing to 
determine their behaviour as regards producing spores. 
We have made a prolonged series of preparations of all three Wheats, 
and find that inoculation and infection occur very readily in the susceptible 
form, the sections showing scores of entries of the germ-tubes : the hyphae 
then pursue the normal course, are typically stout, branched, and contain 
hundreds of nuclei. They also form numerous haustoria, and the attacked 
cells show no evident signs of injury to the chlorophyll-corpuscles or nuclei 
until a late stage of growth. It was particularly evident that the hyphae 
show no signs of degeneration until the period when spore-formation 
begins ; but a tendency of the smaller nuclei to become massed together 
may be observed from about the sixth day onwards. 
The microscopic examination of the ‘ immune J form yielded some very 
curious results. 
It was evident, from the number of entries we found, that the uredo- 
spores germinate and send tubes into the stomata as frequently, or nearly 
so, as they do into the susceptible Wheat. Moreover, the course of events 
is at first similar : so much so that I thought at first that we were either 
mistaken in the information received as to the behaviour of these plants 
in the open, or that the so-called immunity was a mere delusion. 
The behaviour of these hyphae after the fourth to sixth day, however, 
gave us the clue to the mystery. 
In the first place the hyphae do not extend far from the point of 
infection, and they diminish in diameter ; moreover, the contents become 
granulated or almost fibrous and present a starved appearance, while the 
nuclei not only diminish in size and number, but especially in distinctness 
and staining capacity, so that it often appears as if they were absent. 
In short, these hyphae show evident signs of degeneration in all 
respects, and we conclude, from comparison with experimentally starved 
hyphae, that they are undergoing death-changes owing to one of two 
events, viz. they are either starving for want of food-supplies, or they 
are being poisoned. 
Even more striking are the changes observed in the cells of the host in 
the immediate neighbourhood of these degenerating hyphae. 
In the susceptible Wheat, even where the hyphae are particularly large 
and abundant, and full of nuclei and deep-staining protoplasm, the adjacent 
cells, including those into which haustoria have been sent, are still turgid 
