392 | ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
one of the ablest of these students of the alge, at first regarded the 
multicellular body, formed at the germination of the oospore of Cido- 
gonium and Coleochete, as an asexual phase comparable with the 
simple sporophyte of the liverwort Riccia. Celakowsky (1886) distin- 
guishes as homologous alternation those cases, in alge like Ulothrix 
or Hdogonium, where the gamete-producing generation seemed capa- 
ble of zoospore production also. ‘The constant and regular alternation 
of the archegoniates and seed plants he called antithetic alternation. 
Pringsheim (1877) found that moss protonemata form from cuttings 
of the seta of the sporophyte as weil as from bits of the gametophyte. 
From this fact, and from Farlow’s discovery (1874) that a sporophyte 
of the fern, Pteris cretica, may arise directly from the prothallus, with- 
out the fertilization or even the formation of an egg, Pringsheim con- 
cluded that both generations of the archegoniates are really identical. 
He says (1877), p. 6: 
I believe the moss sporogonium stands to the moss plant in the same relation that the 
sporangium-bearing Saprolegnias do to the oogonium-bearing plants of thisspecies, . .. 
I therefore turn against this interpretation of the fruit generation of the thallophytes in 
general, and especially against this interpretation of the sexual shoot generation of the 
Floridese and Ascomycetes . . . The cystocarp is evidently not a separate individual 
but part of the sexual plant that produces it. 
The antithetic view was reasserted, however, especially by Cela- 
kowsky (1877) and Bower (1890), both of whom emphasized the sug- 
gestion of A. Braun (1875) that the sporophyte is a new thing phyloge- 
netically. Bower holds that the types of sporophyte found in the 
archegoniates have arisen by the amplification of the zygote, with the 
sterilization for vegetative functions of smaller or larger portions of 
the originally all-pervading sporogenous tissue. The amphibious type 
of alternation of the mosses and ferns has arisen, according to Bower’s 
conception, with the migration of these plants to the land, and the 
assumption of the terrestrial habit by the sporophyte. The antithetic 
view was also supported in a most striking way, later, by the results 
of the workers on chromosomes. 
The homologous view of alternation also has not been without sup- 
porters in the years since Pringsheim. One of its upholders, Klebs 
(1896), based his belief on the fact that he could determine the type of 
reproductive cells formed by the algee Hydrodictyon and Vaucheria, 
by changing the conditions under which they are grown. Lang (1896-— 
1898) favored the homologous view because of the discoveries of Far- 
low, De Bary, Bower, Farmer, and himself on apogamy and apospory. 
Scott, one of the strongest advocates of the homologous alternation 
theory, bases his belief not only on the evidence afforded by the cases 
of apogamy and apospory, but also on the fossil record. He points 
out the lack of any sporophyte, living or fossil, that can be regarded 
as ancestral to that of the ferns. In arguing for the homologous 
