Nitella, Chara) have only a zygotic type of life cycle (are only gametophytes), then consideration should be given to how this rather simple type of life cycle could have been modified into that of a land plant with a diplobiontic life cycle and sporic meiosis.
There is no supposition, or really even viable possibility, of a preexisting sporophyte in Bower's (1908, 1935) antithetic (interpolation) theory of origin of alternating generations; nor, for that matter, would such be expected based on careful scrutiny of the life cycle of Coleoehaete and other advanced charophytes (Chara, Nitella, etc.
Only the antithetic theory (of sporophyte origin), not the homologous theory, is actually tenable given the possibilities offered by the life cycles of Nitella, Chara, and Coleochaete (as representative of forms ancestral to land plants).
In the case of Chara and Nitella, these charophytic algae produce only gametes (do not produce spores); hence, spore flagellar loss need not even be contemplated in the case of these two advanced charophytes; in others words, it is possible that earliest land-plant spores were never flagellated.
2001), based on nuclear SSU rDNA sequences, the placement of Coleochaete and Klebsormidium is somewhat closer to primitive land plants than is that of Nitella (and Chara); some of their results from chloroplast SSU rRNA genes, in fact, place Klebsormidium closer to land plants than even Coleochaete (echoed in the maximum likelihood tree based on combined data).
Nitella and Chara, as discussed, do not produce spores and are compelling to consider in a putative antithetic development of the land-plant sporophyte; spores of primitive land plants show no evidence of flagellation, or even residual flagellation.
Lee's (1999) conception is based in part on the work of Okuda and Brown (1992), showing a close relationship between the cellulose-synthesizing complex of Coleochaete scutata and that of hornworts, for example, but not those of mosses and tracheophytes--the cellulose-synthesizing complexes of mosses and tracheophytes being more similar to such complexes in Nitella and Chara.