30 Ward . — Recent Researches on the Parasitism of Fungi. 
Massee (109), in an interesting summary of experiments on chemotaxis 
with certain Fungi, in which he confirms previous results, goes so far as to 
say that ‘ infection is due to positive chemotaxis/ and that immunity is due 
to the fact that the plant,* owing to the absence of the chemotactic substance 
in its tissues necessary to enable the germ-tubes of the Fungus to penetrate, 
remains unattached’ (p. 23). 
But, apart from the fact that chemotaxis is also a factor in saprophytic 
life, and that the entrance of a hypha into a stoma is only a preliminary 
act, not necessarily indicative of parasitism, there are other objections to 
the title of Massee’s paper, ‘ On the Origin of Parasitism in Fungi.’ 
Miss Gibson, in my laboratory, has shown that the germ-tubes of 
almost every Uredine she tried will enter quite the wrong host by the 
stomata, as the annexed table shows: — 
Spores. 
Species of Fungus. 
from 
Host. 
Result. 
Uredospores 
Uredo chrysanthemi 
Chrysanthemum 
sinense 
R. Ficaria 
Enter freely. 
Aecidiospores 
Phragmidium rosae-alpinae 
Rosa 
yy 
>> » 
>> 
Uromyces poae 
Ranunculus 
repens 
yy 
j > >5 
yy 
Aecidium bunii 
Bunium 
yy 
Negative. 
yy 
Puccinia poarum 
Tussilago 
Caltha 
Enter freely. 
Uredospores 
Uromyces geranii 
Geraniu??i 
>} 
Aecidiospores 
Puccinia Menthae 
Mentha 
yy 
Enter not very 
freely. 
Uredospores 
Puccinia 
Carduus 
yy 
Enter freely. 
Aecidiospores 
Phragmidium Sanguisorbae 
Poteriu)?i 
yy 
2 or 3 doubtful 
entries. 
Uredospores 
Puccinia glumarum 
Triticum vulgare 
yy 
1 certain entry. 
yy 
Puccinia graminis 
Poa aspera 
yy 
Enter freely. 
yy 
Uromyces poae 
Poa praiensis 
yy 
yy 
Puccinia taraxaci 
Taraxacum 
Tropaeolum 
>> >> 
yy 
Coleosporium Sonchi 
Tussilago 
>> 
>) )> 
yy 
yy yy 
Puccinia pulverulenta 
yy 
Valeriana 
’> » 
yy 
Epilobiu 7 n 
?> 
1 entry. 
yy 
„ Centaureae 
Centaurea nigra 
yy 
Enter freely. 
yy 
„ Menthae 
Mentha 
yy 
» }) 
It cannot be too clearly understood that the entry via a stoma is not 
infection. Over and over again I have found leaves which are immune, 
penetrated at hundreds of stomata without effect. This is why I have 
taken to speaking of the germ- tube and appressorium , formed outside the 
stomata, as distinct from the sub-stomatal or infection-vesicle and -tube 
developed later, in successful cases, in the respiratory cavity beneath the 
stoma. 
Infection proper depends on two sets of factors. On the one hand the 
relations between host and parasite, involving the power of attack by 
means of enzymes and toxins of the latter, and the power of resistance, by 
means of anti-bodies, &c., of the host. On the other hand, the effects of 
the environment on both parasite and host. 
