385 
filtered out and could not be a chemical ferment, for it is opposed to all 
known peculiarities of enzymes to be filtered out of solutions. The 
common method for the concentration of an enzyme, i. e., precipita¬ 
tion with not too strong alcohol from the crude juice and resolution in 
water, was tried. This led to no substance which had infective power. 
Inoculations with heated sap led to the following results: Persistent 
warming at 00° did not perceptibly alter the infectious power; at 65° 
to 75° it was weakened. Heating the sap at 80° for several hours killed 
the infective power. These experiments show that the infective sub¬ 
stance satisfies the requirements of an organized ferment, and indi¬ 
cate that the infective body must be searched for among the small 
organized bodies. Fungi are much too large to pass through filter 
paper, and if the disease was due to these it would seem that they must 
assume at some stage some more easily visible form. 
The following is a rather literal rendering of the author’s conclu¬ 
sions: 
(1) The “ mosaic disease” of tobacco is a bacterial disease, the infective 
organism of which has not yet been isolated so as to know its form and 
mode of life. 
(2) The infective power of the disease from plant to plant under the 
artificial conditions of sap mixture has been established with certainty. 
Under natural conditions there is no plain infection from plant to plant. 
The seeds of diseased plants can produce sound plants. 
(3) The cause of the disease must be sought in the earth of the 
tobacco fields and the hotbeds, for particular fields, especially those in 
which tobacco follows tobacco, are most exposed to the disease. A 
case of transportation of the disease with earth, however, was not 
established. 
Rotation-of crops is advised, also the removal of the diseased plants, 
and after harvest all remnants of the crop. —Erwin F. Smith. 
Moeller, H. —Entgegnung gegen Frank , betreffend den angeblichen 
Dimorphism us der Wurzelknbllchen dcr Erbse. <Ber. d. Dent. 
Bot. Ges., Bd- x, Nov. 24, 1892, pp. 508-570. 
In a recently published note upon root tubercles, Frank states that 
those of the pea show two forms that differ externally, but have the 
same internal structure, and furthermore that the content is different, 
being albumen bacteroids in the one, and amylodextrin bacteroids in 
the other. 
The author of this paper proved some time ago that these tubercles 
do not contain amylodextrin, but a waxy substance, and this lact 
made him doubt the correctness of Frank’s observations. He has also 
studied the exterior form of such tubercles and states that vigorous 
specimens of pea show a considerable variety ol such tubercles, but 
without any distinction ot two special forms. An examination ot their 
contents gave oidy albumen bacteroids. These investigations were 
