1921] SCHERTZ—MOTTLING 125 
how the yellow pigments in the leaf may increase at the expense 
of the chlorophyll. 
Bacteria 
The leaves of Coleus were examined closely for the presence of 
bacteria. In the healthy green leaves a few bacteria of the coccus 
type were observed, while in the fully mottled leaves many bacteria 
of this type were found. A few of the bacillus type were also 
present in the cells. The presence of ammonia and nitrite can 
possibly be accounted for by their activity. Plates were made of 
the leaves under sterile conditions so as to get only those bacteria 
which were inside the cells, and always a much greater bacterial 
count was obtained from the mottled leaves. It is realized that 
the bacterial side of this question is really a problem in itself, and 
that this phase of the subject ought to be further investigated. 
The juice of the mottled leaves was placed on the under side 
of the healthy green leaves and rubbed around; in other cases, in 
addition to rubbing the juice on the leaf, the veins were injured 
mechanically. The leaves in these cases mottled no sooner than 
did the leaves of the untreated plants, and they mottled in exactly 
the same manner as untreated plants. The writer believes that 
the bacteria get a better hold as the leaf weakens from nitrogen 
starvation. Evidently the organism present is a denitrifying one, 
which develops somewhat in the green leaf, and as the leaf weakens 
or mottles the organism develops more rapidly. 
It will be worth while to summarize what other workers have 
discovered about certain bacterial and physiological diseases which 
in some respects appear to be similar to the mottling of Coleus. 
FREIBERG (18) inoculated varieties of pumpkins, squash, water- 
melon, cucumber, citron, muskmelon, and others, and not a single 
infection resulted from his inoculations, yet during the same season 
other plants of these same varieties contracted the mosaic disease. 
JAGGER (24) and DoorrrrLe (13) report that the mosaic leaf disease 
of cucumber is transmissible by rubbing the healthy plants with 
crushed diseased leaves, and have proved that Aphis Gossypi 
transmits the mottled leaf disease of the cucumber. SMITH 
and Boncquet (45) state that Eusettix tenella is the only carrier 
