Application of Horton's first and second laws of branching to fungi

Abstract

A total of 183 colonies representing 14 species of fungi were examined for their agreement with Horton's laws of branch number and of branch length. Most conformed to the law of branch number, an inverse regression of logarithm of branch number per order on branch order. Only a minority of the colonies conformed to the law of branch length, a direct regression of logarithm of mean branch length per order on branch order. More of the colonies were well described by the regression of mean branch length on branch order, and more still by the regression of mean branch length on logarithm of branch order. Branch ratios for colonies were found to vary widely within an isolate and the value of single determinations is questioned. The calculation of length ratios for growing fungal colonies is considered to be valueless. The significance of these findings is discussed in relation to stage of colony development and differentiation.