Cytogenetics of Polyploids III. Dauermodifications in Ageratum conyzoides Linn

The term "dauermodifications' was coined by Jollos in 1913 and he described it as a change induced externally by an experimental means at a definite moment (Jollos 1921). Sonneborn (1950) regarded dauermodifications as the traits induced by environmental conditions, manifesting temporary cytoplasmic inheritance. Hence, after some period, under the original conditions, the induced traits disappear and the original form reappear in the organism. Chandrasekhran and Parthasarthy (1960) regard dauermodifications as the changes induced by the environment that persists for several generations but gradually diminish and disappear. Singh (1964) regards dauermodifications as environmentally induced phenotypic traits that lead to an immature death of the organism: The premature death of the organism is generally regarded to be due to the lethal genes. Presently the term has been applied to the phenotypic changes induced, externally that gradually diminish in subsequent generations and finally disappear, under the original conditions. A lack of cytogenetical work in understand ing the phenomenon prompted the present investigations.