. A practical course in botany, with especial reference to its bearings on agriculture, economics, and sanitation. Botany. CRYPTOGAMS 319 only the dark teleutospores are produced. These remain on the culms in the stubble fields over winter, ready to begin the work of reproduction in spring. For this reason the teleutos are popularly known as " winter spores " in contra- distinction to the uredos, or " summer spores," whose activity is confined to the warm months. It was formerly supposed that black rust was caused by a different fungus from that producing red rust, and to i
. A practical course in botany, with especial reference to its bearings on agriculture, economics, and sanitation. Botany. CRYPTOGAMS 319 only the dark teleutospores are produced. These remain on the culms in the stubble fields over winter, ready to begin the work of reproduction in spring. For this reason the teleutos are popularly known as " winter spores " in contra- distinction to the uredos, or " summer spores," whose activity is confined to the warm months. It was formerly supposed that black rust was caused by a different fungus from that producing red rust, and to it the name Puccinia was given. This has been retained as a general designation for all fungi undergoing these two phases, and the par- ticular form of fungus that we are now con- sidering is known in all its stages as Puccinia graminis. 361. The nonparasitic stage. — The for- mation of teleutospores completes that por- tion of the life history of the fungus during which it is parasitic on wheat and grasses of different kinds. In spring they begin to germinate on the ground, each cell producing a small filament, from which arise in turn several small branches. Upon the tip of , each of these branches is developed a tiny tospore germinating sporelike body called a sporidium (Fig. 454), ^ns °™romSPCoui^ which continues the generation of the rust ter's "Plant struc- fungus through the next stage of its exist- ence. The filament which bears these sporidia is not para- sitic, but when the sporidia ripen and the spores contained in them are scattered by the wind, there begins a second parasitic phase, which forms the most curious part of this strange life history. 362. The aecidium. — Examine next the under side of some barberry leaves (or comfrey, etc., if orange leaf-rust is used) for clusters of small whitish bodies that appear under the lens like little white corollas with yellow anthers in the center. Examine a section of one of these under the. Please note that these
Size: 1016px × 2459px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorand, bookcentury1900, bookdecade1910, booksubjectbotany
