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Studies on The Growth of Lichens I Lobe Formation and the Maintenance of Circularity in Crustose Species

Published online by Cambridge University Press:  28 March 2007

D.J. Hill
Affiliation:
Department of Botany, University of Bristol, Bristol BS8 1UG, U.K.

Abstract

The rate of lobe division during thallus enlargement in Xanthoria elegans and Diploicia canescens is considered in geometric terms. The frequency of lobe engulfment by neighbouring lobes was measured, was fitted graphically to a simple equation and was found to result from constant lobe division with thallus size. Values for a constant in the equation and derived from the observed frequency of lobe engulfment provided a measurement of a new morphological parameter: ratio lobe length to width. Greatest departure from circularity in small thalli of D. canescens occurred when thallus size did not permit lobe competition. Increasing lobe engulfment and thallus circularity in larger thalli appeared to be correlated. Circularity in crustose thalli without lobes is discussed with definitions of ‘primary’ and ‘secondary’ areoles.

Type
Research Article
Copyright
Copyright © British Lichen Society 1984

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