Studies in the Physiology of Parasitism. VII. Infection 
of Berberis vulgaris by Sporidia of Puccinia graminis. 
BY 
W. L. WATERHOUSE, B.Sc. (Agr.), 
Walter and Eliza Hall Agriculture Research Fellow of the University of Sidney. 
( From the Department of Plant Physiology and Pathology , Imperial College of Science and Technology , 
London.) 
With nineteen Figures in the Text. 
A GOOD deal of attention has of late been paid to the mode of infection 
of host plants by certain fungi. Blackman and Welsford (1) showed 
that in the case of Botrytis cinerea the entry of the parasite was not 
brought about by the dissolution of the cuticle of the host, as previous 
workers had supposed, but was due to the mechanical pressure exerted by 
the germ tube. Dey ( 2 ), working with Colletotrichum lindemuthianum , 
obtained similar results. The previous work bearing on the subject of 
cuticular penetration is referred to and summarized in these two papers and 
need not be referred to here. 
The present investigation was carried out to determine whether in 
such a widely different form as Puccinia graminis, Pers. entry into the host 
was brought about in the same way. 
The mode of infection of the wheat plant by uredospores of P . graminis 
through the stomata has already been carefully worked out (3). This work 
followed on a similar investigation by Marshall Ward dealing with the 
related form P. dispersa , Erikss. (4). An investigation of the entry into the 
host of the aecidiospores and uredospores of a number of other rusts was 
carried out by Miss Gibson (5). Little, however, appears to have been 
done in connexion with the details of sporidial infection in any rust fungus. 
Eriksson ( 6 ) refers to the mode of entry of the sporidia of P. Malvacearum 
into the hollyhock in the following terms : “ Wahrscheinlich infolge einer 
auflosenden Einwirkung des Korpers selbst auf die Epidermiswand bildet 
sich an dem Kontaktpiinktchen ein sehr feines, kaum sichtbares Loch, 
durch das sich der Inhalt des Korpers hineinergiesst ’ (p. 75 ). 
[Annals of Botany, Vol. XXXV. No. CXL. October, 1921. J 
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