. Diseases of plants induced by cryptogamic parasites; introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae. Plant diseases; Parasitic plants; Fungi. 288 USTILAGINKAE. Ust. perennans liostr.^ This smut or dust-brand occurs frequently in the Howers of Arrheiiafhcnmi clatius (Fig. 157). The mycelium perennates in the rhizome. An Ustilago nearly allied to the preceding one occurs also on Fcdnca prateiisis, Lolium 'prrennc, and other grasses. The Smut of Barley. There are really two species of Ustilago found on barley, ¥ui. \i>^.—Ustilago perennans. Spore-culture Tj
. Diseases of plants induced by cryptogamic parasites; introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae. Plant diseases; Parasitic plants; Fungi. 288 USTILAGINKAE. Ust. perennans liostr.^ This smut or dust-brand occurs frequently in the Howers of Arrheiiafhcnmi clatius (Fig. 157). The mycelium perennates in the rhizome. An Ustilago nearly allied to the preceding one occurs also on Fcdnca prateiisis, Lolium 'prrennc, and other grasses. The Smut of Barley. There are really two species of Ustilago found on barley, ¥ui. \i>^.—Ustilago perennans. Spore-culture Tj„f 7,,.,.,/,,; .,,-,,] JT^f ^,,i,]r, in plum-gelatine, (v. Tubeuf del.) ^^''- I^-OUIU ,inU Uhl. nUUa. Ust. hordei (I'ers.) {Ust. Jrmcni Itostr.) (Britain and America). This has black spherical spores (6*5 to 7"5ya in diameter), which germinate and give off conidia from a promycelium. The spikelets gene- rally remain enclosed in their coverings. Treatment of seed- corn with a half per cent, copper steep is a certain remedy. Ust. nuda (Jens.) ( America). In ears diseased by this smut the epidermis of the glumes is early lost, so that the spore-powder lies freely exposed when the ears emerge from the leaf-sheath. The spores on germination give off' a four- celled promycelium, which however produces no conidia, but develops directly to a septate mycelium. The spores are smooth-coated and oval (5-7/>t long and 5-6'5yU broad); they are matured and set free at the flowering season of the barley, and probably infect seedlings in spring. The spores of this smut are very resistant against treatment with copper steeps, and it is recommended to soften the barley for several hours in cold water before applying Jenson's method. Ust. tritici (Pers.) (Britain and America). Wheat-brand. The spores are developed in the ovary of the wheat, and are black with a tinge of olive-green. On germination they im- mediately form a non-septate mycelium (Fig. 160). Heniiing'^ has
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