PLATE a 
A. —Plants of the Green Mountain variety exhibiting two types of mosaic symp¬ 
toms, grown in greenhouse, i, showing marked spindling habit and reduced leaf 
surface accompanied by wrinkling and mottling, the extreme type. 2, foliage nearly 
normal as to development but with the characteristic mottling, the mild type. Both 
plants are from mild mosaic parentage but from different hills. 
B. —Young Green Mountain plant showing early the symptoms of extreme mosaic. 
Grown in greenhouse bench (1920-21) from parentage designated as “healthy but 
adjacent to mosaic hills," in the experimental field in 1920. 
C. —Young Green Mountain plant of the extreme type, developing the symptoms 
very early in the greenhouse bench (1920-21), from parentage designated as mild 
mosaic in the experimental field in 1920. From the same tuber as A, 1. 
D. —Young plant apparently healthy at first but later developing mild mosaic 
symptoms. From mild mosaic parentage and from the same seed tuber as A, 2. 
