<P> The evidence of plant evolution changes dramatically in the Ordovician with the first extensive appearance of spores in the fossil record ( Cambrian spores have been found , also ) . The first terrestrial plants were probably in the form of tiny plants resembling liverworts when , around the Middle Ordovician , evidence for the beginning of the terrestrialization of the land is found in the form of tetrads of spores with resistant polymers in their outer walls . These early plants did not have conducting tissues , severely limiting their size . They were , in effect , tied to wet terrestrial environments by their inability to conduct water , like extant liverworts , hornworts , and mosses , although they reproduced with spores , important dispersal units that have hard protective outer coatings , allowing for their preservation in the fossil record , in addition to protecting the future offspring against the desiccating environment of life on land . With spores , plants on land could have sent out large numbers of spores that could grow into an adult plant when sufficient environmental moisture was present . </P>
<P> The evidence of plant evolution changes dramatically in the Ordovician with the first extensive appearance of spores in the fossil record ( Cambrian spores have been found , also ) . The first terrestrial plants were probably in the form of tiny plants resembling liverworts when , around the Middle Ordovician , evidence for the beginning of the terrestrialization of the land is found in the form of tetrads of spores with resistant polymers in their outer walls . These early plants did not have conducting tissues , severely limiting their size . They were , in effect , tied to wet terrestrial environments by their inability to conduct water , like extant liverworts , hornworts , and mosses , although they reproduced with spores , important dispersal units that have hard protective outer coatings , allowing for their preservation in the fossil record , in addition to protecting the future offspring against the desiccating environment of life on land . With spores , plants on land could have sent out large numbers of spores that could grow into an adult plant when sufficient environmental moisture was present . </P>
when do bryophytes ( including mosses liverworts and hornworts ) first appear in the fossil record
when do bryophytes ( including mosses liverworts and hornworts ) first appear in the fossil record
around the Middle Ordovician
around the Middle Ordovician