Bibliographical note

Seeds of D. majalis (collected from a population in North Zealand, Denmark) were germinated in vitro with a compatible fungus, Tulasnella calospora. Germination itself was almost completely inhibited in long and short day photoperiods and at a very low light intensity, but initial illumination (particularly with red light) raised the eventual germination percentage. These responses would tend to enhance germination in open vegetation but below ground, where there are chances of immediate symbiotic infection and little risk of desiccation. Germination in vitro was highest at about 20°C with little diurnal fluctuation. Above 25°, seeds remained imbibed but did not germinate and rejected fungal infection. Symbiotic seedlings grew well at fairly low temperatures and responded to chilling (5° for 15 weeks) by developing an aerial shoot and later a tuberoid. These findings suggest that the seeds normally germinate in autumn when saprophytic nutrition of the mycelium is optimal. The requirement of a cold season for further seedling differentiation may be restrictive for the distribution of this species.