19*7] CURRENT LITERATURE 245 



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Mosaic disease of tobacco. — Allard 15 has recently presented good evi- 

 dence to combat the theory of Woods and of Heintzel that oxidases are 

 responsible for the mosaic disease of tobacco, in which he showed that the 

 disease was dependent upon a specific infection. A more recent paper by 

 Allard 16 describes in detail a study of the properties of the so-called "virus" 

 of the mosaic disease of tobacco. Healthy plants were inoculated with the 

 virus after filtration through a Livingston atmometer porous cup, after fil- 

 tration through powdered talc, after precipitation with ethyl alcohol, after 

 treatment with formaldehyde, with hydrogen peroxide, with precipitates of 

 aluminum and nickel hydroxides, and after subjecting the virus to high and 

 low temperatures. Plants were inoculated also with water extracts of the 

 dried mosaic tobacco, made after extracting with ether, chloroform, and other 

 solvents. The infectious principle was retained by filtration through Living- 

 ston atmometer porous cups and by powdered talc, although the filtrates 

 gave intense peroxidase reactions. Alcoholic solutions of 75-80 per cent 

 destroyed the infective principle, while 45-50 per cent solutions did not, but 

 carried down the infectious principle with the precipitate. Virus treated 

 with one part formaldehyde in 800-1500 parts of solution gave an infection. 

 Stronger solutions gave no infection, although they still gave strong 

 peroxidase reactions. Ether, chloroform, carbon tetrachloride, toluene, and 

 acetone failed to extract either the infective principle or the peroxidase 

 from dried material. The virus was killed at temperatures near ioo° C, 

 but when subjected to a temperature of — 180 C. for 15 minutes it was 

 not weakened. In every case controls were carried out with tap water and 

 with the untreated virus. From the results the author concludes that 

 neither enzymes nor the constituents of healthy sap can be responsible for the 

 disease, and that since the pathogenic agent is highly infectious and capable 

 of increasing definitely, there is every reason to believe that it is an ultra- 

 microscopic parasite of some kind. — H. R. Kraybill. 



Fossil Osmundaceae — Kidston and Gwynne-Vaughan 17 have described 

 three species of fossil Osmundaceae, two of which are respectively from the 

 Tertiary of Spitzbergen and of Queensland. Another species, Osmimditcs 

 Carnieri, between the Tertiary and Jurassic of the Andes of Paraguay, is most 

 interesting. The authors add something to the original descriptions of Schus- 

 ter from whom they received their material. The stem unfortunately is not 

 well preserved, but the endodermis frequently joins around the margins of the 

 leaf gaps, and an internal phloem was also probably originally present. The 



Allard 



U.S. Dept. Agric. Bull. 40. 



1914. 



i6 



virus 



Jour 



Agric. Research 6:649-674. 1916. 



■» Kidston, R., and Gwyxne-Vaughax, D. T., On the fossil Osmundaceae. 

 Part V. Trans. Roy. Soc. Edinburgh 50:460-480. ph. 4^44- i9 l6 - 



