. Diseases of plants induced by cryptogamic parasites : introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae . Plant diseases; Parasitic plants; Fungi. 364 UREDINEAK. direction; their sori form dark spots which break out from beneath the epidermis. The yellow uredospores have a coat beset with fine spines, and are given off from sori which may or may not be enclosed in a peridium. The sori of the aeeidium-stage have no peridium, and are known under the generic name of Caeoma; they frequently occur on other hosts than those of the teleutospores. Pycnidia are produce
. Diseases of plants induced by cryptogamic parasites : introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae . Plant diseases; Parasitic plants; Fungi. 364 UREDINEAK. direction; their sori form dark spots which break out from beneath the epidermis. The yellow uredospores have a coat beset with fine spines, and are given off from sori which may or may not be enclosed in a peridium. The sori of the aeeidium-stage have no peridium, and are known under the generic name of Caeoma; they frequently occur on other hosts than those of the teleutospores. Pycnidia are produced in little yellow patches. Melampsora tremulae Tul. (Britain). The sori of uredo- spores appear as little yellow protuberances on leaves or young shoots of Fopuhis tremula. The dark-brown patches of teleuto- spores appear later on the under epidermis, and where they. Fig. 196.—Caeoma pinitarquuvi. Section showing four pycnidia, from one of whicli (sp) numerous conidia are being discharged. Ccwojna-patcbes are developing beneath the cortical layer, as yet unbroken. (After R. Hartig.) occur in large numbers, an early fall of the leaf may result. The teleutospores hibernate in dead leaves on the ground. In spring the sporidia germinate and infect young shoots of Pinus sylvestris, producing the disease known as Caeoma pinitorquum} This disease attacks pine-seedlings, appearing generally on the needles. It is most frequent in plantations from one to ten years old, rarer in those of ten to thirty years, and not as yet observed in older. Pinus sylvestris is most commonly attacked, but it has also been observed on Pinus montana in Jutland. After formation of the Ca€owa-patches, the young thin shoots generally die off, but thicker ones become twisted at the place attacked, whence the name " pine-twister " commonly given to this disease. If the leading shoot be attacked, the seedlings may succumb altogether. The disease develops rapidly, 1R. Hartig, Wichtige Krankheilen d.
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