450 LEVINE: CROWN GALL ON BRYOPHYLLUM 
plant, which forms leafy crown galls readily. Three distinct 
types of crown galls appear here also, namely, the common 
globular type, the differentiated globular type which forms 
small and slowly growing leaflets over its surface, and the axillary 
leafy crown gall which consists of a crown gall and a poorly 
developed axillary bud. The stimulus to growth of this type 
of crown gall is not the direct result of B. tumefaciens, but is 
due rather to a mechanical interference with the food supply 
incident to the development of the mass of crown gall tissue. 
In a recent paper (Levine 1924) the author reports further 
observations on rubber trees, which were studied for a period of 
over four years. The results substantiate his earlier studies 
made on- the Bryophyllum and the tobacco plants. 
De Vries (1891), Goebel (1908) and Loeb (1915, 1917, 1918) 
have claimed that the development of shoots in the notches of 
the Bryophyllum leaf was inhibited by the presence of the main 
root or regenerated roots on the stem. These authors further 
claimed that the organic separation of the leaf from the rooted 
part of the plant acts as a stimulus upon the leaf and induces 
growth of the buds in the notches. Loeb (1915) contends that 
this is not the only factor involved. He states that a piece of 
stem, even if it does not form any roots but only a shoot, will 
prevent or greatly delay the growth of the notches of a leaf 
connected with it. 
Miss Braun (1918) pointed out that leaves of Bryophyllum 
attached to the plant were capable of producing leaves and roots 
at their notches. Loeb (1918 b) claims that this development 
occurs only in sick plants. He contends that the recumbent 
position of the stem acts as a partial block to normal trans- 
portation of fluids, and that such sick and bent stems behave 
to all purposes like isolated pieces of stems, the leaves of which . 
will give rise to shoots. Reed (1923) holds that, while the stem 
and roots of the plant do not influence the development of the 
budsin the leaf notches, conditions, such as the absence of light,and 
the abundance of very moist air or water, do have such an effect. 
The present report deals with further observations on the 
effect of inoculations of Bacterium tumefaciens into the notches 
of leaves of Bryophyllum. I showed that in leaves which were 
stimulated to shoot development by being cut from the stem 
and planted in moist sand, relatively few leafy crown galls 
