. A textbook of botany for colleges and universities ... Botany. 84 MORPHOLOGY teleutospores, the saprophytic promycelium or basidium bearing ba- sidiospores, and the parasitic mycelium bearing aecidiospores), lives upon two unrelated hosts, and produces four (perhaps five) kinds of spores. It is natural that such a polymorphous plant should not have been understood at first, and that the different phases should have received different names. The mycelium bearing uredospores was named Uredo ; that bearing teleutospores, not known at first to be the. Fig. ig6. — Wheal rust: an aecidium (cluster
. A textbook of botany for colleges and universities ... Botany. 84 MORPHOLOGY teleutospores, the saprophytic promycelium or basidium bearing ba- sidiospores, and the parasitic mycelium bearing aecidiospores), lives upon two unrelated hosts, and produces four (perhaps five) kinds of spores. It is natural that such a polymorphous plant should not have been understood at first, and that the different phases should have received different names. The mycelium bearing uredospores was named Uredo ; that bearing teleutospores, not known at first to be the. Fig. ig6. — Wheal rust: an aecidium (clustercup) arising froni the mycelium of the barberry leaf, and showing the rows of aecidiospores. — After Chamberlain. same mycelium, was named Puccinia; and the form parasitic on the bar- berry was named Aecidium. Now the name Puccinia is retained for the plant, and the other names are used for convenience in designat- ing the respective stages. Not all rusts include two hosts in their life history, and it is usual to distinguish rusts as autoicous (those having one host) and heteroicous (those having more than one host). Alternation. — Recently the nuclear changes in the life history of wheat rust have been traced. In the«aecidium, the cell which produces a row of aecidiospores contains two nuclei, the second nucleus having entered it from an adjacent cell of the mycelium. In the subsequent cell divisions the two nuclei divide independently, so that each aecidiospore contains two nuclei. This binucleate condition con-. 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; Barnes, Charles Reid, 1858-1910, joint author; Cowles, Henry Chandler, 1869- joint author. New York, Cincinnati [etc] American book company
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