Studies of the Ballistics of Ascospores

Abstract

SUMMARYThe ballistics of horizontal spore discharge in fifteen species and two varieties of Ascomycetes have been studied. An apparatus for measuring horizontal discharge is described and formulae derived for the volumes of irregularly shaped spores. The average and maximum distances of discharge for the selected fungi are recorded and include maximum ranges of more than 50 cm for Podospora fimiseda and the 64-spore variety of P. decipiens.An analysis of the relationship between the average distance of horizontal discharge and projectile size shows that the formula d = i^r^ does not hold true for comparisons hetween a large number of unrelated species. If, however, only closely related species, such as those of the genera Podospora and Sordaria, are considered then considerable agreement with the formula is observed.If, in a single species, the relationship between size and distance of discharge of various sizes of spore-projectiles is analysed, the results are in accordance with the formula d = Kr'^ only if there is relatively high separation of the full spore complement into projectiles of different sizes. It is suggested that deviation from the formula occurs because the initial velocity of discharge is not constant for all projectiles.

Studies on the Discharge of Ascospores From Lichen Apothecia

“…The variation in distance of discharge between projectiles of similar size suggests that muzzle velocity and projectile morphology are factors to be considered. These results are thus in agreement with those of Walkey & Harvey (1966), who found that amongst non-lichenized fungi a simple relationship between projectile size and discharge distance could only be detected between closely related species. In no case is the distance of active discharge sufficient to be important in spreading the species to new habitats, and spores are most probably further dispersed by wind.…”

Ascospore Discharge in Hypoxylon

“…Walkey and Harvey (1966) described H. rubiginosum as "a mainly nocturnal species in which spore discharge starts several hours before the end of the light period and falls off before dawn." In continuous light spore discharge gradually became less and after 8 days nearly ceased.…”

“…In their study of species H. multiformis Fr., Walkey and Harvey (1966) suggested that discharge resulted from a delayed response to darkness.…”

Studies on Some Aspects of Ascospore Liberation and Dispersal in Lichens

“…Spore sizes represent the measurements of fifty discharged spores from several different ascocarps of each species. The volume of ellipsoidal spores was calculated using the formulae suggested by Walkey & Harvey (1966): Spore size (|im) Length 18-9 14-9 55-9 16-7 12-5 13-5 The total numbers of spores discharged from all ascocarps per millimetre are shown in Table 2 Table 3 shows the number of spores discharged from five ascocarps after 48 hr under two different conditions of relative humidity and after their subsequent transfer to moist filter paper for a further 24 hr. Lecanora atra, L. carpinea, L. dispersa, Opegrapha atra, Sarcogyne regularis andXanthoria parietina were used in this study but L. atra and L. carpinea failed to produce spores under these conditions.…”