NECROSIS, HYPERPLASIA, AND ADHESIONS IN MOSAIC 
TOMATO FRUITS 1 
By Max W. Gardner 2 
Associate in Botany , Purdue University Agricultural Experiment Station 
INTRODUCTION 
The extremely severe streak or 
winter blight type of mosaic occurred 
in a greenhouse crop of Bonny Best 
tomatoes at La Fayette, Ind., during 
November and December, 1923, and 
an opportunity was afforded to make a 
preliminary study of the structural 
abnormalities exhibited by many of the 
diseased fruits. The disease was char¬ 
acterized by the destructive necrotic 
streaking and spotting of leaves, stems, 
and fruits described in a previous ac¬ 
count (12, p. 8 ): 3 Every one of the 
more than 800 plants in the house also 
evinced on the young leaflets the typi¬ 
cal dark green puffy areas on a lighter 
background, a reliable diagnostic fea¬ 
ture of the mosaic type of disease. 
The mosaic nature of the disease was 
further verified by successful inocula¬ 
tion of healthy tomato seedlings with 
the juice of a young fruit by J. B. 
Kendrick in another house and by 
numerous cultural tests which proved 
the internal fruit lesions to be free from 
bacteria. 
Hundreds of fruits of all sizes and 
ages showing a variety of responses to 
the disease were available for study, 
and unstained free-hand sections of 
fresh material, mostly from very young 
green fruits, revealed most peculiar 
abnormalities in the tissues. The sec¬ 
tions were mounted in water and pre¬ 
served by adding lacto-phenol (equal 
parts of phenol, lactic acid, glycerin, 
and water). Material was also em¬ 
bedded in paraffin, sectioned on the 
microtome, and stained with gentian 
violet, safranin and licht green, 
Haidenhain’s iron-alum liaematoxylin, 
and ZiehFs carbol fuchsin. 
NORMAL ANATOMY OF THE FRUIT 
An acquaintance with certain phases 
of the normal anatomy and develop¬ 
ment of the fruit is a necessary pre¬ 
liminary to a consideration of the 
abnormal. The mature tomato with 
its several-celled ovary and fleshy walls 
and its bulky axile placentae bearing 
the seeds embedded in a pulpy matrix 
of thin-walled parenchymatous tissue 
is familiar to all. A very young ovary 
about 4 mm. in diameter as shown in 
Figure 1, A, differs mainly in that the 
ovules more or less completely fill the 
locular cavity and are not embedded 
in a cellular matrix. During the early 
stages of enlargement of the fruit the 
placental tissue grows out between the 
ovules (fig. 1, B) to form the gelatinous 
matrix of thin-walled parenchyma 
which separates and finally engulfs the 
ovules and completely fills the locular 
cavity (fig. 1, C and D) by the time the 
fruit is about 10 mm. in diameter. 
The placental matrix touches the in¬ 
ner surface of the fruit wall or pericarp 
and the surfaces of the radial locular 
partitions, but remains free from these 
surfaces as well as from the epidermis 
of each ovule (fig. 1, B, C, and 
D). The young fruit enlarges very 
rapidly under greenhouse conditions 
and hence is composed of very active 
meristematic tissue. Figure 1 shows 
that growth must progress with ex¬ 
treme rapidity in the placental matrix 
in the short period during which the 
ovary enlarges to 1 cm. in diameter. 
Later the epidermal cells of the seed 
coat elongate enormously to form a 
palisade layer, which touches but re¬ 
mains free from the placental matrix. 
GROSS ABNORMALITIES IN MOSAIC 
FRUITS 
One of the most conspicuous symp¬ 
toms on mosaic fruits is the eruption 
of brownish, translucent, rather flat- 
topped blisters of various shapes and 
sizes as illustrated in Plate 1, B, and 
in a previous paper (12, p. 8). These 
may later be bordered by a shallow 
peripheral fissure. Large lesions of 
this type may eventually contain nu¬ 
merous cuticular fissures and form 
1 Received for publication July 10, 1924; issued June, 1925. Contribution from the Botanical Depart¬ 
ment, Purdue University Agricultural Experiment Station, La Fayette, Ind. 
2 The writer desires to acknowledge his indebtedness to Prof. H. S. Jackson and Prof. L. F. Heimlich for 
helpful advice and to J. B. Kendrick for assistance. 
7 Reference is made by number (italic) to “Literature cited,” p. 888. 
Journal of Agricultural Research, 
Washington, D. C. 
( 871 ) 
Vol. XXX, No. 9 
May 1, 1925 
Key No. Ind-16 
