Diseases of plants induced by Diseases of plants induced by cryptogamic parasites; introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae diseasesofplant00tube Year: 1897 160 ASCOMYCETES. * Witches' brooms on birch are very common in Scotland. They appear as tangled masses of twigs, which at first sight give the impression of some bird's nest. I have frequently examined the leaves borne on these brooms, and have never failed to find the asci of an Exoascus. Sadebeck gives in his monograph the two above-named species as found on birches bearing ' brooms. Mites {
Diseases of plants induced by Diseases of plants induced by cryptogamic parasites; introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae diseasesofplant00tube Year: 1897 160 ASCOMYCETES. * Witches' brooms on birch are very common in Scotland. They appear as tangled masses of twigs, which at first sight give the impression of some bird's nest. I have frequently examined the leaves borne on these brooms, and have never failed to find the asci of an Exoascus. Sadebeck gives in his monograph the two above-named species as found on birches bearing ' brooms. Mites {cfj. PhyUyjitus) have also been given as the cause of these malformations. On close examination of brooms which undoubtedly bore Exoascus, I found that a broom results from a prolific development of small twigs on one or a few knotty swollen parts of a branch. Each central Fig. (' Broom oftlic Hornbeaia. Exoascus carpini on Belulus. The bush measures about i metre across, and arises laterally from a branch, the upper normal part of which has been removed, (v. Tubeuf phot.) knot we may regard as the position of the Inid which was first infected, and from which the broom system took its origin. As one result of the attack of the fungus, the greater number of the buds in the axils of the scales of the infected bud have grown out as twigs, but not into well-developed ones. In consequence, nearly every twig has been killed back by the winter, but not completely, so that from each twig- Ijase has sprung a new crop of stunted immature twigs like the first, and equally liable to be killed in the following winter. Thus has arisen that tangled mass of dead or sickly birch twigs which we call a witches' broom. [Edit.]
Size: 1517px × 1319px
Photo credit: © Bookend / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: archive, book, drawing, historical, history, illustration, image, page, picture, print, reference, vintage
