446 OHIO EXPERIMENT 
veritable mosiacs. As shown a few years since by Beijerinck, Wood and others, 
these diseases and others of their class show a yellowing of foliage due to oxi- 
dizing enzymes in the leaves. Further as shown in experiments made in 1904, 
(see Bulletin 156) at Germantown, this disease is communicated from one plant 
to another by touching. The experiment included touching a succession of 
plants after touching a diseased plant; these touchings were sometimes repeated. 
During the period of one month there was an increase of 67 percent in those 
touched following contact with diseased plants. This shows the advantage of 
handling mosaic plants at separate times from healthy ones. 
Fig. 95. Roots of seedling tobacco plants from soil inoculated 
with Thielavia basicola: A. Soil sterilized with formalin (1 to 200 
and B. untreated. After Gilbert Bulletin 158, Bur. Plant Ind., U. 
S8.D.A. 
Root-Rot. Root-rot (7hielavia basicola Zopf.) on tobacco was first discov- 
ered by the writer upon plants received from Clermont county in 1899; since this 
time it has been more or less serious during wet seasons. In the vicinity of 
