a = Po ws = Ee 
172 BACTERIA IN RELATION TO PLANT DISEASES. 
“Let us take such an emulsion and add some drops of it to two tubes: one containing the normal 
diastasic liquid, the other the same quantity of this liquid boiled. They are put into the thermostat 
.at 38°. Of these two tubes, equally cloudy, the check after some hours remains cloudy, while the 
other has become almost completely transparent.” 
There is no precipitate and therefore the clearing can not be ascribed to agglutination. 
“Ainsi Dictyostelium mucoroides ne peut se développer qu’avec des Bactéries; il est parasite des 
colonies bactériennes; ses myxamibes ingérent les Bactéries et les digérent dans leurs vacuoles a 
l'aide d’une diastase dont l’action est assez semblable a celle de l’amibodiastase.” 
Similar results were obtained with other species, 7. e., Dicty. purpureum, and Polysphondylium 
violaceum, showing that these also are bacterial parasites. 
These Acrasieae are strictly aerobic. As soon as a tube is sealed growth ceases. The amount 
of humidity greatly influences the morphology of the sporophores. ‘The optimum temperature for 
growth is between 22° and 25°. Above 28° there is no development. They will grow at a tem- 
perature as low as 8° but then very slowly. 
The morphology and the color of the Myxomycete are both changed by changes in the sub- 
stratum, e. g., if Bacillus subtilis is added to mixed cultures of Dictyostelium mucoroides and Bact. 
fluorescens, the sporophores are longer and branched forms are frequent. 
Under some circumstances bacterial.pigments are absorbed by the living Myxomycetes. The 
author holds that certain Acrasieae described as distinct from Dicty. mucoroides on account of their 
variation in color are only the same species associated with different chromogenic bacteria. These 
bacterial pigments therefore have a taxonomic importance in the Acrasieae. Grown with “Bact. 
fluorescens the young fructifications of Dicty. mucoroides are fluorescent and the old ones are color of 
a dead leaf; grown with B. coli the fructifications of this species are pure white and remain so. When 
Polysphondylium violaceum, which has a pigment of its own, is grown in the presence of Bacterium 
violaceum its color becomes paler, the pigments of the two being chemically dissimilar bodies. 
Similar results as regards necessity for living bacteria were obtained with Didymium difforme 
and D. effusum. 
So far as the writer has observed bacteria always occur in the club-root of crucifers 
along with Plasmodiophora brassicae. 
ONE BACTERIUM WITH ANOTHER. 
This subject is a very large one and no attempt has been made to cover it either in 
the text or bibliography. 
According to Beyerinck and Van Delden their Chroococcum assimilates nitrogen only 
when it enters into symbiosis with other bacteria—Granulobacter, Aerobacter, etc. 
In 1906, Keding published his Weitere Untersuchungen. He found Azotobacter 
not only on the surface of Fucus and several other salt water alge, but in dune sand near 
the roots of strand plants, and in all investigated soils, except moor soil. Azotobacter 
is able, he says, to assimilate the nitrogen of the air in pure culture, and this ability was 
not increased by growing it in combination with other bacteria. The sea forms of the 
organism can grow in the presence of 8 per cent salt. 
According to Bottomley “Pseudomonas radicicola and Azotobacter, together make a 
powerful combination for the fixation of free nitrogen.’’ These are both said to have been 
isolated from the algal zone of the root-tubercles of cycads. He inoculated oats, barley, 
hyacinths (galtonia), and parsnips with mixed cultures. Best results with oats which were 
nearly doubled in weight. 
Thomas F. Manns (The Blade Blight of Oats; a bacterial disease. Agr. Exp. Sta., 
Ohio, Bull. 210) has stated that a widely prevalent disease of oats is due to a symbiotic 
relationship between two species of bacteria. 
