114 BOTANICAL GAZETTE [JANUARY 
of reaction between the two and not to the antiseptic properties of the 
formaldehyde. This explanation he finds further supported by the fact that 
the infective power of extracts from diseased plants is not destroyed by treat- 
ment for two days with concentrated solutions of ether, chloroform, carbon 
tetrachloride, toluene, acetone, and glycerine. In this connection it is well to 
remember a statement by Smirx® that in a number of organisms tested by 
him 1o grew in the presence of chloroform (5 cc. of chloroform in test tubes 
with 1o cc. of milk or beef bouillon), and 2 grew vigorously in the presence 
of thymol. He further states that, ‘‘in the opinion of the writer, statements 
of physiologists respecting the existence of enzymes in the tissues and fluids of 
higher plants must be taken with much allowance when chloroform, thymol, 
and similar antiseptics have been depended upon to keep the solution free 
from bacteria. A medium to which chloroform or thymol has been added must 
be shut in and shaken continuously if the full antiseptic value of these sub- 
stances is to be obtained.” 
Microchemical tests showed starch and sugar present in greater amounts 
in the dark green than in the chlorotic areas. FREIBERG suggests that this con- 
dition, taken in connection with the specificity of reaction between formal- 
dehyde and the infective principle, and the possibility that formaldehyde _ 
is one of the first products of photosynthesis, may form a basis upon which the 
physiological nature of mosaic diseases may be explained. The possible rela- 
tion of these factors to the formation of an enzyme is not made clear. Neither 
is it made clear how an enzyme can “reproduce itself.” If it does so, why is 
not ALLARD’s contention the better one, that the causal agent is an organism 
and not an enzyme? And if it bé granted for the sake of argument that the 
ea ie of the leaves is caused by an enzyme, the question of the origin of 
the enzyme is still unanswered. In the work of ABERHALDEN and of KNUDSON, 
cited by FREIBERG, the development of proteolytic enzymes or of tannase was 
not spontaneous, but resulted from a stimulus foreign to the organism. 
Yellows or wilt, a serious disease of cabbage in many parts of the country, 
has recently been investigated by Gillman.’ He finds that the causal fungus, 
Fusarium conglutinans Wollenw., has a high optimum temperature and is very 
resistant to drying, both in pure culture and in the soil. The characteristic 
symptoms of the diseases are dependent on a temperature of about 17-22° C. 
or above for their occurrence. Lower temperatures (12—16° C.) under con- 
trolled conditions prevented the occurrence of the trouble in the greenhouse. 
[wo rusts of economic importance, Puccinia coronata Cda. and P. Sorghi 
Schw., are the subject of a physiological investigation by Mars.’ The 
§ Smitu, E. F., Bacteria in relation to plant diseases. Ann. Mo. Bot. Gard. 1:74, 
75. 1905. 
9 GILLMAN, JosePH C., Cabbage yellows and the relation of temperature to its 
occurrence. Ann. Mo. Bot. Gard. 3: 25-8. 
7 Marys, E. B., The relation of some rusts to the physiology of their hosts. 
Amer. Jour. Botany 4:179-221. 1917. 
