. I funghi che causano malattia vegetale . Le malattie delle piante; funghi. B. amylovorus (Burr.) De Toni. (Numero del gruppo 221. 0-.) Bacillus in brodo, 0,9-1,5 x 0,7-1,0 fi, più a lungo quando i vecchi. Il Gram positivo; nessuna capsula; flagelli diversi; no spore; brodo offuscato, pellicola leggera. La gelatina mostra lento, crateriform lique- fazione. Agar, sepolto colonie bianco, colonie di superficie elevata, circolare wet-shining, margine irregolare. Il latte coagulato in tre quarti di un giorno più tardi digerito in un condizione pastosa. Opz. 25-30°. T. D. P. 43,7°, 10 min. Faculta- tivo i anaerobe. Indol prodotta; nessun gas; nessun suino- mento. I batteri w

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. The fungi which cause plant disease . Plant diseases; Fungi. B. amylovorus (Burr.) De Toni. (Group number 221. 0—.) Bacillus in broth, 0.9-1.5 x 0.7-1.0 fi, longer when older. Gram positive; no capsule; flagella several; no spores; broth clouded, pellicle slight. Gelatine shows slow, crateriform lique- faction. Agar, buried colonies white, surface colonies elevated, circular wet-shining, margin irregular. Milk coagulated in three-fourths of a day, later digested to a pasty condition. Opt. 25-30°. T. D. P. 43.7°, 10 min. Faculta- tive anaerobe. Indol produced; no gas; no pig- ment. Bacteria were noted in blighted pear twigs by Fig. 23.—b. amyio- BuTrill in 1877.*'' *' In 1880 he ^* demonstrated rn"'by'"fisifon? *^^ communicability of the disease by intro- After whetzei ducing the bacterial exudate into healthy pear trees as well as into apple and quince trees. This constitutes the first case of plant disease definitely at- tributed to bacteria. Burrill's results were confirmed by Arthur in 1884 *^ by one hundred and twenty-one puncture inoculations, using the exudate, also a bacterial suspension from diseased twigs. He further demon- strated the susceptibility of Juneberry and haw- thorn. Usually the disease appeared about a week after inoculation. Attempted raspberry and grape inoculations failed. Arthur placed the whole matter on a firm foun- dation by passing the bacteria through a long series of artificial cultures and then by'inocular tions, showing that they were capable of causing the blight.*^'«' He further demonstrated that the bacterial exudate from the tree, when freed of bacteria by filtration, could not produce disease. The results of an extensive study of the bacteria on various media; of their morphology and stain reactions were pubUshed by Arthur in 1886.«* Bacteria were shown to penetrate twigs 3-4 dm. beyond their area of visible effect.^"' In 1902 Jones ^ isolated an organism from blighted plum trees.. Fia. 24.—Claw from

Parole chiave associate all'immagine

• bookcentury1900
• bookdecade1910
• booksubjectfungi
• bookyear1913