48 Ward.— Recent Researches on the Parasitism of Fungi. 
results to the heteroecism of the Rusts of Wheat, but also in the proof that 
the uredo-stage is by itself capable of specialization on particular species 
and races of Wheat, &c. My experiments with the Bromes showed the 
same thing for various well-recognized species and varieties within 
this genus with the uredo of a particular form-species of Puccinia 
dispersa. 
Returning to the bearing of these matters on the relatively immune 
wheat described on p. 37 (A. Rivet Wheat), we see that it is in no degree 
immune in the sense of being able to prevent the germ-tubes from entering 
the stomata, or even to keep the infection-tubes from attacking the 
mesophyll-cells. What seems to occur is that the cells attacked, usually — 
but not always — succumb at once to some influence, poisonous or other- 
wise, exerted by the hyphae, and the latter find themselves involved in 
the ruined debris of these cells. This is an inimical environment for 
such hyphae, and they die off. Sometimes, indeed, the poisonous action 
of the Fungus seems to be exerted at the very surface of the leaf. 
Unfortunately, although we are justified in assuming the existence of 
poisons or enzymes in the Fungus, no one has as yet established the fact of 
their presence in these Uredineae. 
De Bary (24) and I myself showed long ago (196) very convincingly that 
such poisons and enzymes occur in other parasites — e. g. Botrytis — and 
numerous observers have proved the existence of about a dozen different 
kinds of enzymes in various other Fungi, but I failed to extract any such 
body from P. dispersa (190), and Dr. Green, who at my suggestion has under- 
taken the investigation of spores and mycelia of Puccinia glumarum , has 
also as yet failed to obtain results beyond the probability that diastase 
occurs, and possibly cytase also. However, since Dr. Green is continuing 
this work, we may hope that he will eventually be able to throw more 
light on the matter. 
Now it is interesting to observe in this connexion that we frequently, 
and indeed usually, find c immune ’ plants flecked with small yellow or 
orange spots. Miss Gibson has recently observed the same kind of thing 
on leaves of an ‘ immune ’ form of Chrysanthemum she was trying to infect 
with Chrysanthemum Rust during the recent hot weather. 
That these flecks are due to the dead tissues shining through appears 
certain from our examination of a number of cases, and I find that such 
flecks of corroded tissue in which infection has failed have been observed in 
the open by other observers. My remarks on p. 298 of the paper ‘ On the 
Relations between Host and Parasite in the Bromes and their Brown Rust ’ 
(190) refers to the same phenomena. 
Moreover, Klebahn states (98, p. 36 ): ‘ Keimschlauche und Nahrzellen 
sterben ab, und in Folge der Braun- oder Rotfarbung des Inhalts der Nahr- 
zellen erscheinen braune oder rote Flecken an den Impfstellen. So 
