The identity of Elaphomyces granulatus

Abstract

Thed istinction between Elaphomyces granulatus Fr. and E. asperulus Vittad. has been variously interpreted by recent investigators. A consideration of the relevant literature shows that Vittadini (1831, 1842) gave no clear description of spore ornamentation but stated that fruit bodies of E. asperulus were darker in colour than those of E. granulatus and that the peridium of the latter was uniformly light coloured in section, that of E. asperulus being reddish. Examination of a large number of collections from different sources showed that spore ornamentation is variable even within the same fruit body. Younger spores tend to be spiny, relatively small and light coloured, older ones irregularly warty, large and dark. The outer layer of the walls of young spores in freshly collected material consists of radiating rod-like elements embedded in a matrix. As the spore enlarges these separate (the spore then appearing spiny) and in the final stages of spore maturation the matrix dies and shrinks causing the ‘spines’ to coalesce and partially collapse (the spore then appearing as if covered with irregular warts). Experiments on the effects of rate of drying of fruit bodies revealed that the proportion of spiny spores decreases with drying. It is concluded that E. asperulus cannot be distinguished from E. granulatus on the basis of spore ornamentation alone, and is best treated as a variety of the latter.