i5 2 
The Ohio Naturalist. 
[Vol. XIII, No. 8 , 
green regions seem slightly swollen, while the yellow areas appear 
appreciably thinner. Many of the affected leaves become crinkled 
or show an irregular growth; this is due to an uneven tissue ex¬ 
pansion; the healthy green regions develop more rapidly than 
the yellow areas, hence a warping or crinkling results. Woods 
(1902) states that in very severe cases the entire plant may become 
so deformed that it is almost unrecognizable. 
As the plant becomes older and the flower buds form, there 
may appear what is known as “mottle top,” although the plant 
may have remained perfectly healthy up till flowering time. Ac¬ 
cording to Sturgis (1899), weather conditions may bring on the 
disease at this time and affected plants may recover if conditions 
become favorable again. He regards “mottle top” as a later 
stage and milder form of calico; the typical mosaic appearing 
only in the earlier stages of plant development. The writer has 
occasionally encountered this in the field and from his observation 
it does not seem serious, as it apparently involves only a few of 
the uppermost leaves, which are always removed at topping 
time. 
Tomato .—Where tomatoes are forced under glass, mosaic 
disease is not uncommon and appearances similar to mosaic are 
also found in the field. One of the first investigators to call 
our attention to the mosaic disease on tomato was Sturgis (1899). 
He cites a case where a field of tomatoes was overtaken by an 
early frost and severely nipped. As a result of this artificial 
pruning, the disease made its appearance. Woods (1902) pro¬ 
duced the disease at will on tomato and poke weed by severely 
pruning healthy plants. See his plates 2, 5 and 6. Tomato 
chlorosis and its infectious properties are discussed by Clinton 
(1908). Hunger (1905) seems to be the first foreign investigator 
who worked with tomato mosaic. He confirmed Woods’ (1902) 
pruning results, having used plants grown from seed from various 
countries. Westerdijk (1910) carried out extensive experiments 
with tomato mosaic, which show the disease is inheritable. According 
to her the disease is conspicuous on stalks and fruit as well as 
leaves. She says that the stalks frequently show a spiral band of 
yellow color. During the earlier stages of fruit development, 
while it is still green she says, that the yellow spots are easily 
recognized, but as the fruit matures, the deep red masks them. 
The yellow areas on the leaves, as for tobacco, seem con¬ 
fined more or less to the tissues between the main veins. The 
dark green regions nearby seem to assume a rather “over healthy ” 
aspect. Here again, an unequal growth of tissues cause the leaf 
to warp or curl. In severe cases, descriptively termed, “fern 
leaf” appears. Here the main veins are considerably hyper¬ 
trophied, while the intermediate tissues altogether fail of develop¬ 
ment, giving the leaf a very striking dissected appearance. 
