New YorK AGRICULTURAL EXPERIMENT STATION. 153 
of the enzym through the intermediate tissues as was ob- 
served by de Barry (1886) in the case of Peziza and by others 
with similar parasitic invasions. When this first came to 
our attention it suggested the possibility of testing the dif- 
fusibility of the enzym through some medium impenetrable to 
the bacteria, partly as confirmatory of the above explanation 
and partly as another method of studying the action of the 
enzym apart from the organisms. Before we got to the point 
of undertaking this, however, van Hall’s (1902: 649) paper 
came to hand in which he describes his similar attempts and 
their very interesting results. In his studies upon his Bacillus 
omnivorus he employed a modification of the plan developed 
by Beijerinck in his studies upon the mosaic disease of to- 
bacco. Van Hall’s method consisted in growing his organism 
in streak cultures upon the surface of agar, then cutting off 
a surface layer from this, carrying the streak, and transplant- 
‘ing the layer to potato. In this way he secured the softening 
of the potato underneath the streak. In other cases he re- 
moved sterile bits of agar underlying the culture and trans- 
planted them to sterile vegetable surfaces for trial. | 
We found the method outlined in the following experiment 
a more convenient way of securing the same result. 
Beet broth agar, two per cent, was poured into small petri 
dishes to a depth of about 3 mm. When this had hardened 
_ and the surface dried slightly, Bacillus carotovorus was im- 
planted on the surface of a small area at the center. At the 
end of three days a good surface growth was thus secured 
about 1 cm.'in diameter. A slice somewhat larger than this 
layer of agar was then cut from the interior of a fresh turnip 
root and placed in a large sterile petri dish, using caution to 
avoid contamination. The layer of agar from the smaller 
dish was then carefully lifted with sterile instruments and 
placed upon the surface of this turnip slice in the larger dish 
and covered to prevent contamination. This was designated 
A. The details of the method may become clearer upon ex- 
amination of the accompanying figure. Two other dishes, B 
and ©, were prepared in like manner at the same time. A 
laver of sterile agar was laid in a fourth dish upon a turnip 
slice as a control and designated D, 
