R}:S1STAXT PLAXTS ITQCj 



cage : Pollenia rudis Fabricius ; Empoasca mali Le Baron ; Psylla pyricola 

 Forster ; Plagio^nathits polilus Uhler and Sapromyza bispina Loew. 



Although the insects were entirely at liberty to go from one plant to the 

 other, the disease was unable in any case to spread from the infected 

 to the healthy plants. This is probably due to the fact that sucking insects 

 are not able to produce lesions of the tissues such as would facilitate pene- 

 tration of the Bacillus. 



There are insects which are nmch more active in this direction, although 

 fairly few in number ; the}- are : false tarnished plant bug {Lygus invitus 

 Say) ; and the apple red bugs {Heterocordylus malinus Renter and Lygidea 

 mendax Renter). The possibility of the bacilli penetrating into the plant 

 through the lesions caused by these insects cannot be dismissed. 



933 - On the Susceptibility of Phaseolus vulgaris and P. multiflorus to Bean resistant 

 Rust (Uromyces appendicu/atus) and other Fungoid Diseases. — i^akon plants 



Ceoug., in Ztitschri ft fur Pflanzcnkrankhtitin, Vol. 26, Xo. 2, pp. S3-M;, Stuttgart, 1016. 



Mycological literature indicates no specific differences between Pha- 

 seolus vulgaris and Phaseolus midtiflorits as regards their susceptibility to 

 bean rust. The experiments of the present writer however show that such 

 specific differences do exist. He studied several kinds of beans belonging 

 to these two species, which are grown in his garden, where rust was ver>- pre- 

 valent the year before. The plants affected were: 3 varieties of P. fmdtiflonis, 3 

 climbing varieties of P. vulgaris and one variety of P. vulgaris nanus ; the}- 

 were so near to each other that the possibility of infection was the same 

 for all the plants. 



At the end of the summer when the fungus appeared in consequence 

 of the intense formation of teleutospores, a dift'erence was observed in the 

 susceptibility of the different plants. It was noted that the plants were 

 either strongly attacked by the parasite or else free from fungi. This phe- 

 nomenon was first of all ptit down to characteristics inherent in the vari- 

 eties. Move thorough studies showed indeed that P. vtdgaris was alone 

 attacked, while P. muUiflorus was quite free. The dift'erence was so great 

 that later on it was possible to distinguish one species from the other merely 

 by the presence or absence of the parasite ; these results were also confinued 

 by subsequent botanical examination. 



These observations were completed with the aid of more abundant 

 material. A large number of kitchen-garden plants at Hohenheini and 

 environs w^ere first of all studied, and it was found that Phaseolus multi- 

 florus was exempt, while P. vtdgaris was always strongly attacked. Att- 

 ention was next given to a large number of varieties of beans grown in 

 the Botanical Garden of Hohenheini, namely : 7 different kinds of P. 

 multiflorus ; 37 dift'erent varieties of the climbing form of P. vtdgaris and 24 

 dift'erent kinds of P. vulgaris nanus. A minute study of each of the leaves 

 of all these specimens disclosed the following facts : 



i) all the specimens of climbing forms of P . vtdgaris were strongly 

 attacked and covered with teleutospores of the fungus ; 



2) Among the 24 varieties of P. vtdgaris nanus, S had all specimens 

 strongh- attacked and 13 had all their individuals free ; 



