May 1,1925 
Necrosis, Hyperplasia, and Adhesions in Tornadoes 
883 
areas which may result in severe and 
extensive cracking. Cracking of the 
tubers has also been reported by 
Barrus and Chupp (6, p. 125). Murphy 
and McKay (22, p. 351) have recently 
reported similar blisters on tubers of 
the President variety in which they 
found evidence of cell division and a 
later necrosis and collapse of the cells. 
The occurrence of translucent tissue 
in mosaic diseases or related troubles 
has been recorded by many observers. 
Bailey (5, p. 150), in 1892, noted dark 
translucent spots on tomato leaves 
affected with winter blight, and Orton 
and McKinney (23, p. 242 ) observed 
transitory watery blisters on tomato 
leaves which soon collapsed and were 
replaced by necrotic spots. Brandes 
(7, p. 10) found that there were water- 
soaked mosaic lesions on sugar cane 
stalks which were followed by longi¬ 
tudinal cracks, and Kunkel (17, p. 3) 
noted translucent spots in the very 
young leaves and translucent strips 
within the stalks of mosaic corn plants. 
Atanasoff (4, p. 6) noted translucent 
margins about the leaf and stem lesions 
of potato stipple streak, and Hunger- 
ford (16, p. 136) working with a similar 
disease, noted that the lesions were 
first watersoaked. 
Dickson (10, p. 48) found that the 
lighter leaf areas were more translucent 
in a number of mosaic diseases includ¬ 
ing tomato, tobacco, potato, legumes, 
and raspberry and attributes this to the 
presence of less chlorophyll and to a re¬ 
duction of intercellular space owing to 
the smaller, more isodiametric and 
closely packed cells, a condition which 
would facilitate the passage of light. 
This condition was described by Woods 
(34, p. 10) in the light areas of mosaic 
tobacco leaves and has also been ob¬ 
served by Doolittle (11, p. 17) in cu¬ 
cumber mosaic, by Rand (26, p. 14) in 
pecan rosette, and by Matsumoto (19 
p. 295) in azuki-bean mosaic. Rand 
also found decreased intercellular space 
in the thickened, dark green leaf areas. 
It would seem, therefore, that the for¬ 
mation of translucent tissue with re¬ 
duced intercellular space is rather com¬ 
mon in the mosaic types of disease. 
Necrotic spotting of the leaves and 
necrotic streaking of the stems seem to 
be of rather general occurrence among 
mosaic diseases. Internal necrosis, how¬ 
ever, is not so generally recorded but 
has been noted by Smith and Boncquet 
(32, p. 104) in the phloem in beet 
curly top, by Artschwager (2, p. 569) 
in the phloem tissue in potato leaf- 
roll, by Robbins (29, p. 355) in the 
midrib phloem in sugar beet mosaic, 
and by Rankin (27, p. 38) in the phloem 
and pericycle in raspberry leaf-curl. 
Isolated, scattered, internal pockets or 
strips of necrotic tissue have been found 
by Matz (20, p. 75) in the stem paren¬ 
chyma in mosaic sugar cane, by Kunkel 
(17, p. 5) in the stem parenchyma in 
corn mosaic, and by Gttssow (IS, p. 
493), Murphy (21, p. 79), Barrus and 
Chupp (6, p. 125), Atanasoff (4, PP- 7 
and 11), Artschwager (3, p. 242), and 
Murphy and McKay (22, p. 351) in the 
case of potato streak and related dis¬ 
eases. In sugar cane and corn, cavi¬ 
ties were found associated with the 
necrotic strips and pockets. 
In the tomato, Orton and McKinney 
(23, p. '241) noted internal necrotic areas 
in the stem, and Howitt and Stone (14, 
p. 163) state that the brown “discolora¬ 
tion extends deeply into the flesh of the 
fruit and can be traced from the epider¬ 
mis along the septa to the center.” 
Paine and Bewley (24, P- 188) found 
necrotic patches in the pith and cortex 
of the stem and in the petiole. Brittle- 
bank (8, p. 232) also found the brown¬ 
ish lesions in the case of spotted wilt 
extending deeply into the fruit. The 
latter observers intimate, however, that 
the internal necrosis extends inward 
from the surface lesions, whereas in our 
material there was ordinarily no such 
direct connection between external and 
internal lesions. 
Hypertrophy is reported by Dickson 
(10, p. 34) in the palisade parenchyma 
of the thickened, dark green areas in the 
EXPLANATORY LEGEND FOR PLATE 6 
__ 0 _ r __„ _ ^abepidermal necrotic plane accompanied by marked 
hypertrophy of the adjacent cells, and a rupture of the pericarp which extends almost to the surface. The 
placental matrix with its necrotic surface plane is pressing against and adhering to the pericarp. Photo¬ 
micrograph X 33. Stained with carbolfuchsin. Fruit 12 mm. in diameter 
D.—A necrotic region in the axial tissue of the fruit showing the collapse of the necrotic cells and the 
hypertrophy of the surrounding cells forming the translucent zone visible under the hand lens. Photo¬ 
micrograph X 33. Stained with carbol fuchsin. Fruit 12 mm. in diameter 
