<P> Envelope - enclosed spore tetrads are taken as the earliest evidence of plant life on land, dating from the mid-Ordovician (early Llanvirn, ~ 470 million years ago), a period from which no macrofossils have yet been recovered . Individual trilete spores resembling those of modern cryptogamic plants first appeared in the fossil record at the end of the Ordovician period . </P> <P> In fungi, both asexual and sexual spores or sporangiospores of many fungal species are actively dispersed by forcible ejection from their reproductive structures . This ejection ensures exit of the spores from the reproductive structures as well as travelling through the air over long distances . Many fungi thereby possess specialized mechanical and physiological mechanisms as well as spore - surface structures, such as hydrophobins, for spore ejection . These mechanisms include, for example, forcible discharge of ascospores enabled by the structure of the ascus and accumulation of osmolytes in the fluids of the ascus that lead to explosive discharge of the ascospores into the air . </P> <P> The forcible discharge of single spores termed ballistospores involves formation of a small drop of water (Buller's drop), which upon contact with the spore leads to its projectile release with an initial acceleration of more than 10,000 g . Other fungi rely on alternative mechanisms for spore release, such as external mechanical forces, exemplified by puffballs . Attracting insects, such as flies, to fruiting structures, by virtue of their having lively colours and a putrid odour, for dispersal of fungal spores is yet another strategy, most prominently used by the stinkhorns . </P> <P> In Common Smoothcap moss (Atrichum undulatum), the vibration of sporophyte has been shown to be an important mechanism for spore release . </P>

Name three ways that spores are different from seeds