. Diseases of plants induced by cryptogamuc parasites; introduction to the study of pathogenic fungi, slime-fungi, bacteria, and algae. English ed. by William G. Smith. Plant diseases; Parasitic plants. 364 UREDINEAE. 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 wliich may or may not be enclosed in a peridium. The sori of the aecidium-stage have no peridium, and are known under the generic name of Caeoma; they frequently occur on other hosts than those of the teleutospore
. Diseases of plants induced by cryptogamuc parasites; introduction to the study of pathogenic fungi, slime-fungi, bacteria, and algae. English ed. by William G. Smith. Plant diseases; Parasitic plants. 364 UREDINEAE. 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 wliich may or may not be enclosed in a peridium. The sori of the aecidium-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 Populus tremuld. The dark-brown patches of teleuto- spores appear later on the under epidermis, and where they. Jr^o' Fig. 196.—Cneoma pinitorquum. Section showing four pycnidia, from one of which {!<p) numerous conidia are being discharged. Cai/ouirt-patches are developing beneath tlie 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 Finns sylvestris, producing the disease known as Cacowa i^initorquum} 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. Finns sylvcstris is most commonly attacked, but it has also been observed on Finns montana in Jutland. After formation of the CVifcowr^-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,
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectparasit, bookyear1897
