126 BOTANICAL GAZETTE Mees [FEBRUARY 
of the disease-producing agent of the curly leaf of sugar beet. 
STEWART and Reppick (46) report that the mosaic disease of 
beans is transmitted through the seeds, and that healthy seedlings 
rubbed with crushed diseased leaves showed infection four weeks 
later. McCuirintock (36) noticed that several varieties of lima 
beans mottle, while the larger variety growing with these does not 
mottle. He thought that the bean mosaic disease was carried by 
the seed. Epson and SCHREINER (15) state that OrTON observed 
a potato disease characterized by bronzing and later browning of 
the leaf. This disease appeared in New Jersey, but was absent in 
areas which were treated with potash or stable manure. They 
believed that the primary cause was insufficient potash or per- 
haps an excess of nitrates in the presence of a minimum potash 
supply. 3 
BoncQuEt (5) found that the mottled leaf of beets, tobacco 
leaves, mottled potato leaves, and many other mottled leaves were 
associated with bacteria. The normal green leaves of these plants 
gave no nitrite or ammonia tests, while usually the mottled leaves 
showed the presence of nitrites and free ammonia. The fact that 
a leaf is yellow, however, is no sign that nitrite or ammonia is 
present in it. Boncquet thought that the mottling of the leaves 
was a pathological disturbance brought about by the partial and 
local nitrogen starvation of the tissues. Nitrogen starvation in 
the leaves around nitrate-reducing foci explained the mosaic nature 
of the leaf diseases in which an abundance of nitrite was detected. 
Potato plants growing in soil rich in nitrate may yellow and mottle, 
owing to the presence of nitrate-reducing bacteria in abundance. 
Summary 
1. The leaves of Coleus Blumei (var. Golden Bedder) are very 
prone to mottling or loss of chlorophyll. Mottling progresses 
from the lower leaves upward. Mottling of the leaves takes place 
first at the edge of the leaf and progresses slowly toward the veins 
and to the base of the leaf. Usually the pair of leaves immediately 
above these mottles next, and so on as the plant grows. 
2. In mottling the chloroplasts lose their green color, become 
reduced in size, and carry on very little photosynthesis. 
