538 



SCIENCE 



[N. S. Vol. XLIII. No. 1111 



leaves. The fourtli plant developed mosaic 

 again, but not as seriously as before treat- 

 ment. Healthy plants inoculated with the 

 juice of leaves from the first three plants con- 

 tracted the disease ahnost without exception, 

 as they did from the fourth plant, which 

 showed the disease. Here we have a case of 

 apparent recovery, but the plants still con- 

 tained the active principle of the disease in a 

 very infectious form. The percentage of in- 

 fection from these plants is given below: 



From plant 'No. 1, 8 healthy plants developed 

 6 cases of mosaic in 18 days, 75 per cent. 



From plant ISTo. 2, 8 healthy plants developed 

 8 cases of mosaic, or 100 per cent. 



Prom plant No. 3, 10 healthy plants devel- 

 oped 9 cases, or 90 per cent. 



From plant ISTo. 4, which showed a slight 

 trace of the mosaic, 100 per cent, infection was 

 secured. 



These results show that when blue light is 

 used, there is a suppression of the leaf color 

 variation more or less permanent in character, 

 the treated plants with one exception showing 

 no typical symptoms of the disease for at least 

 two weeks subsequent to the removal of the 

 hoods. It can not be said, however, that the 

 disease was controlled, as inoculation of 

 healthy plants with juice from diseased leaves 

 produced the trouble in nearly every case. 

 The active principle of the disease was stiU 

 present in apparently normal, fully recovered 

 leaves, and was highly infectious. 



These experiments were repeated and the 

 same results obtained in practically every case. 

 They do not entirely harmonize with the re- 

 sults obtained by Lodewijks, but do in so far as 

 the plants under the blue hoods showed an 

 apparent recovery; but as Lodewijks, so far 

 as the wi'iter is aware, did not try any re- 

 inoculation experiments, he overlooked the 

 fact that the active principle might still be 

 contained in the leaves and that it might be 

 capable of transmission. This is clearly shown 

 in the above experiments, and there is no 

 doubt that the active principle of the disease 

 is still present in plants treated in this man- 

 ner. It is evident that the treatment of 

 plants as above recorded does not destroy the 



active principle, whatever may be its character, 

 the treated leaves apparently still containing 

 it, very probably in the same manner as do 

 parts of the plant which do not show visible 

 symptoms of the disease normally, such as the 

 stem, lower leaves and roots — the juices of 

 which are often highly infectious. 



More detailed results of these experiments 

 are to be published later in connection with 

 a report of work on the mosaic disease of 

 tobacco as carried on at this station. 



George H. Chapman 



Massachusetts Agricultural 

 Experiment Station 



THE NATIONAL ACADEMY OF 

 SCIENCES 



At the annual meeting of the Academy to be 

 held on April 17, 18 and 19, the program of the 

 scientific sessions wUl be as follows: 



Auditorium, National Museum. Public scien- 

 tific session for the reading of papers. 



On Permeability of Endothelia: S. J. Meltzeb. 

 The Influence of Morphin upon the Elimination of 



Intravenously Injected Dextrose: I. S. Kjleiner 



and S. J. Meltzeb. 



Th^ Sex of a Parthenogeneti-c Frog: Jacques 



Loeb. 



It seemed of interest to determine the sex of 

 frogs produced by artificial parthenogenesis. The 

 first experiments in this direction by Loeb and 

 Bancroft had been made on a frog and a tad- 

 pole of about four months old. The gonads of 

 both sexes contain eggs at that age and it was 

 only with approximate certainty that the sex of 

 our parthenogenetie specimens could be deter- 

 mined. As far as we were able to judge the sex 

 in the two cases referred to was male. The 

 writer has since succeeded in keeping a number of 

 parthenogenetie frogs alive for about one year 

 and one of them was recently killed and the 

 gonads sectioned and examined. They were found 

 to be testicles containing well-developed sperma- 

 tozoa. This confirms the former statement of 

 Loeb and Bancroft that the frogs produced by 

 artificial parthenogenesis are males. 



Finer Mechanisms of Protection from Infection: 



Simon Flexner. 



The biological phenomena associated with re- 

 covery from bacterial infections among animals 

 remained largely unexplained until the era which 



