. A text-book of botany for secondary schools. Botany. Fig. 141.—The winter spores of wheat-rust. means of these summer spores the rust may spread through a field of wheat and into adjoining fields with great rapidity. Later in the season, on the stubble and on plants not removed in the har- vesting, black lines and dots appear, which are masses of a very different kind of spore sent to the surface by the myce- Uum (Fig. 141). This spore, which is two- celled and has a very heavy wall, is the winter spore; for it is in this form that the rust usually endures the winter. In the spring the winte
. A text-book of botany for secondary schools. Botany. Fig. 141.—The winter spores of wheat-rust. means of these summer spores the rust may spread through a field of wheat and into adjoining fields with great rapidity. Later in the season, on the stubble and on plants not removed in the har- vesting, black lines and dots appear, which are masses of a very different kind of spore sent to the surface by the myce- Uum (Fig. 141). This spore, which is two- celled and has a very heavy wall, is the winter spore; for it is in this form that the rust usually endures the winter. In the spring the winter spores, lying where the plants on which they were produced have decayed, begin to ger- minate, each one of the two cells send- ing out a short filament. This filament is not a parasite, but a saprophyte, and usually consists of four cells, each one of which sends out a little branch, at the tip of which a small spore is pro- duced (Fig. 142). These may be called early spring spores. These early spring spores are scat- tered by the wind; and those falling upon barberry leaves germinate, the new mycelia entering and spreading through the leaves. In this phase the rust is parasitic upon an entirely dif- ferent host, and one that holds no relation to wheat. The mycelium in the barberry leaves sends to the leaf surface,. Fig. 142.— a winter spore of wheat - rust germinating, each fila- ment producing four cells, each of which sends out a branch that produces at its tip a spore (early spring spore). — After Tu- Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Coulter, John Merle, 1851-1928. New York, D. Appleton
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