NISHIMURA: A CARRIER OF THE MOSAIC DISEASE ype | 
no symptoms of the mosaic disease whatever could be detected. 
However, inoculation tests demonstrated that the sap of these 
‘plants contained the infective principle of the disease. These 
plants were again taken from the field and transplanted into the 
greenhouse for the winter. Although growth appeared normal 
and symptoms of the mosaic disease could not be detected with 
certainty, experiments showed repeatedly that the infective prin- 
ciple of the disease was still present in the expressed sap. Allard 
further shows that when scions of the immune species, NV. glutinosa, 
are grafted upon mosaic-diseased plants of N. Tabacum the infec- 
tive principle of the disease may pass into N. glutinosa without 
the subsequent development of symptoms in it. 
These experiments bear an interesting relation to my own obser- 
vations on the alkekengi as a carrier of the disease. A so-called 
carrier of the disease is, first, an organism which through acquired 
toleration continues to harbor the germ or virus after recovery 
from the diseased condition; or second, one which through natural 
toleration may acquire and transmit the germ or virus without 
itself showing any symptoms or suffering in any way from the 
disease. A third type of carrier is found in those organisms which 
are immune, but may passively transmit a disease (as does A butilon 
arboreum in Baur’s grafting experiments), without necessarily 
becoming a seat for the multiplication of the germ or the increase 
of the virus. See Baur (1906). 
MATERIAL AND METHODS 
I have used two species of plants as a source of the mosaic 
disease, namely: 
1. Apple of Sodom (Solanum aculeatissimum). The first 
plant of this species showing the mosaic disease was brought from 
Florida by Professor Harper in December, 1915. So far as I am 
aware this plant has not hitherto been reported as showing mosaic, 
though there is of course every reason to suppose that most of 
the species of Solanum are susceptible. The symptoms in apple 
of Sodom include all those enumerated above. 
2. Tobacco (Nicotiana Tabacum). I have used the juice of 
mosaiced plants of the tobacco, kept as stock cultures in the green- 
house of Columbia University. 
