However, the most popular theory of the origin of land plants is that they originated from erect green algae . Some green algae don't release the fertilized egg as in many algae, but allow it to to form a zygote while still attached to the parental plant. The zygote develops into an embryo while retained in and protected by the plant , an important adaptation to live on land. In addition to the zygote being protected by the plant , mitosis to produce a multicellular sporophyte presents the opportunity to produce many spores from a single zygote. Delayed meiosis thus produces amplification of the number of spores produced , a useful adaptation for life under the harsh conditions on land.
Some green algae do have alternation of generations.
Finally, there are a lot of molecular and cellular similarities between green algae, particularly the charophytes, and plants. Green algae and plants both have the thylakoid membranes, intracellular membranes into which the chlorophyll is inserted, stacked into grana. Cell division is very similar in charaophytes and plants. Evolution of the bryophytes and seedless tracheophytes. The diploid sporophytes and the haploid gametophyte would look very much alike.