NOTES AND ABSTRACTS. 
249 
Tobacco Mosaic Disease, a Specific Form of. By H. A. Allard {Jour. Agr. 
Res. vii. pp. 481-7, Dec. 1916 ; pi.). — A few plants of Nicotiana viscosa developed 
mosaic disease in a field. They were further studied and the virus from them 
proved infectious to other plants of N. viscosa and its hybrids with N. Tabacum, 
but not to N. Tabacum. Attempts to infect N. viscosa from N. Tabacum affected 
with mosaic disease proved abortive, and the hybrids between N. viscosa and 
iV. Tabacum also proved immune from the attacks- of mosaic disease when 
inoculated with the virus from N. Tabacum. The hybrids were externally very 
much like the seed parent, N. Tabacum. — F. J. C. 
Tobacco, Some Properties of the Virus of Mosaic Disease of. By H. A. Allard 
(Jour. Agr. Res. vi. pp. 649-674; 1916). — Some investigators have attributed 
the occurrence of mosaic disease of tobacco (and other plants such as tomato) 
to the presence in abnormal quantities of oxidases and peroxidases, but the 
origin of the disturbances which have caused the development of these abnormal 
amounts are somewhat in doubt. The author shows that the infectivity of 
the sap from diseased plants is destroyed by alcohol of 75 to 80 per cent, but not of 
45 to 50 per cent. The peroxidases may be destroyed by hydrogen peroxide 
without adversely affecting the virus. Weak formaldehyde solutions do not 
destroy the virus, but when stronger concentrations are used the solutions are 
no longer infective, although peroxidase reactions may be intense. Ether, 
toluene, chloroform, carbon tetrachloride, and acetone all failed to destroy 
the infectious principle in mosaic leaves, but it is quickly killed at temperatures 
near boiling point of water. The virus is highly resistant to low temperatures, 
enduring a temperature of — 180 0 C. without weakening its infective powers. 
Other observations, together with the foregoing and the fact that mosaic disease 
does not occur in absence of infection, lead the author to conclude that " a 
specific, particulate substance not a normal constituent of healthy plants is 
the cause of the disease. This . . . agent is highly infectious and is capable of 
increasing indefinitely within susceptible plants ... it is an ultramicroscopic 
parasite of some kind." — F. /. C. 
Tomato and Bean Bug. By W. W. Froggatt {Agr. Gaz. N.S.W. vol. xxvii. 
pp. 649-650 ; 1 plate). — The adult Tomato and Bean Bug (Nezara viridula) 
is shield-shaped. It is of a rich green tint, and easily escapes detection on the 
foliage of a tomato plant. The eggs are laid on the surface of the leaves. These 
leaves should be cut off and destroyed. The adults can be shaken off the plants 
on to a sheet. — E. W. 
Vanillin, A Field Test with the Toxic Soil Constituent. By J. J. Skinner 
(U.S.A. Dep. Agr. Bur. Soils, Bull. 164, Jan. 1915). — Vanillin is found as a 
constituent in many plants and soils. When isolated it is toxic to plants in 
varying degrees, according to type of soil and its concentration therein. 
It is demonstrated that while 400 to 500 parts per million of vanillin proved 
harmful in one soil, it had much less effect in another. 
Field results on an area of 8£ square feet gave the following decreases : — 
Cowpeas, 33 per cent, green hay 
» 35 „ pods 
Garden peas, 30 per cent. 
>, 20 „ 
String beans, 336 lb, ; vines, 122 lb, pods from an acre. 
The ill effect of vanillin persisted, and was harmful to plants six months after 
crops were harvested. — C. P. C. 
Vegetable Crops in Porto Rico, Insects Affecting. By Thomas H. Jones 
(U.S.A. Dep. Agr., Bur. Entom., Bull. 192; April 1915; 4 plates). — Upwards of 
thirty-nine varieties of insects attack vegetables in Porto Rico, many of which 
already occur in the United States. Several, however, are not known to be 
present on the mainland. This bulletin is the result of an effort made by the 
Dep. Agr. to obtain information upon obnoxious insects liable to introduction. 
V. G. J. 
Vegetative Succession under Irrigation. By J. F. MacBride (Jour. Agr. 
Res. vi. pp. 741-759 ; August 1916 ; plates). — This is a valuable contribution 
to our knowledge of the changes that occur in vegetation through interference 
with natural conditions. Land periodically flooded in order to "form artificial 
pasturage was studied, and the sequence in which various plants original^ forming 
part of the vegetation were killed out and replaced by Deschampsia caespitosa 
