. Diseases of plants induced by cryptogamic parasites : introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae . Plant diseases; Parasitic plants; Fungi. 476 FUNGI IMPERFECTI. of the shoots, aud either rupture the epidermis or grow out from the leaf-scar cushions (Fig. 297). The couidia are abjointed from filamentous conidiophores inside the pycnidia, and emerge as tendril-like structures. They are two-celled, small, cylindrical, and pointed at both ends. Germination takes place easily in water, and the disease spreads rapidly over the young developing shoots during
. Diseases of plants induced by cryptogamic parasites : introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae . Plant diseases; Parasitic plants; Fungi. 476 FUNGI IMPERFECTI. of the shoots, aud either rupture the epidermis or grow out from the leaf-scar cushions (Fig. 297). The couidia are abjointed from filamentous conidiophores inside the pycnidia, and emerge as tendril-like structures. They are two-celled, small, cylindrical, and pointed at both ends. Germination takes place easily in water, and the disease spreads rapidly over the young developing shoots during May. The mycelium permeates the twig, living both inside the cells and between them. The disease has been observed on Picea excelsa and F. Menziesii, not only in nurseries and on young trees, but also in pole- forest, where it frequents the upper crown and causes death. At the beginning of an attack the pruning of diseased twigs in young plantations should be at- tended to. Septoria nibi (Westend.).^ Blackberry leaf-spot. This is a parasite of some economic importance in the United States, where it interferes with the blackberry culture. It also occurs in Europe and Britain. S. ribis Desm. produces a somewhat similar disease on leaves of currant and gooseberry.^ (Britain and America.) S. piricola Desm. occurs throughout all Europe, causing little greyish spots on leaves of pear trees. It is probably a pycnidial form of Sphaerella lucillae Sacc. S. crataegi Kich. A common species on leaves of Crataegus in Europe. S. cerasina Peck. On leaves of Prunus serotina in the United States. Many forms of Septoria infest cultivated vegetables: S. petroselini Desm. is the cause of dry spots appearing on leaves of ^Description in Bulletin, No. 6, Ohio Agric. Exper. Station, 1891. "Description in Bulletin, No. 13, Iowa Agric. Exper. Station, Fig. 296.—Seploria parasitica, a. Young diseased shout of Spruce, with apex still fresh and green. b. Needle diseased towards base, c,
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