Complex sentence: As goddess of love and sex, Venus played an essential role at Roman prenuptial rites and wedding nights, so myrtle and roses were used in bridal bouquets; but myrtle was not used in the bridal crown because as the marriage itself was under Juno's authority.
Split into simpler sentences: As goddess of love and sex, Venus played an essential role at Roman prenuptial rites and wedding nights, so myrtle and roses were used in bridal bouquets. On the other hand, myrtle was not used in the bridal crown, as the marriage itself was under Juno's authority.