STUDIES IN THE PHYSIOLOGY OF THE FUNGI 
XV. GERMINATION OF THE SPORES OF CERTAIN FUNGI 
IN RELATION TO HypROGEN-ION CONCENTRATION! 
ROBERT W. WEBB 
Formerly Rufus J. Lackland Research Fellow in the Henry Shaw School of Botany 
of Washington University. 
INTRODUCTION 
The effect of the hydrogen- and the hydroxyl-ion concentration 
in a mannite medium upon germination of the spores of certain 
fungi, Aspergillus niger, Penicillium cyclopium, Botrytis cinerea, 
Fusarium sp., and Lenzites saepiaria, and therange within which 
their most favorable germination occurs have been presented in 
a recent paper (Webb, 719). Very striking data were obtained 
from this preliminary study, the features of particular interest 
being (1) the importance of active acidity in germination and (2) 
the relatively low percentage of germination under conditions of 
active alkalinity. It was found, in general, that the majority 
of the fungi employed showed maximum germination of the 
spores with relatively high acidity, namely, Px 3.1, and further, 
that none of the fungi suffered inhibition of germination on the 
acid side of neutrality until a hydrogen-ion concentration greater 
than that of Px 2.8 was passed. Germination quantities in 
most cases decreased, though not necessarily proportionally, 
with decrease in hydrogen-ion concentration from the optimum 
concentration previously mentioned. Certain forms, however, 
such as Penicillium cyclopium and Fusarium sp., exhibited sec- 
ondary maxima at or near neutrality. 
The medium employed in that investigation contained mannite 
as the sole nutrient, and its hydrogen- and hydroxyl-ion con- 
centrations were adjusted by means of equal additions of ortho- 
phosphoric acid and successively increasing additions of sodium 
hydroxide. Logical questions which naturally arise at this 
1An investigation carried out at the Missouri Botanical Garden in the Graduate 
Laboratory of the Henry Shaw School of Botany of Washington University, and 
submitted as a thesis in partial fulfillment of the requirements for the degree of doc- 
tor of philosophy in the Henry Shaw School of Botany of Washington Bp 
(283 
ANN. Mo. Bor. Garp., Vor. 8, 1921 
