Notes on Recent Literature. 
2 16 
than as connected phenomena. If we take this view it is natural 
to suppose that the tetrasporic plant is essentially homologous with 
the sexual plant, while the carposporic phase has been intercalated, 
and is antithetic in the original sense of Celakovsky and Bower, 
which has no reference to the position of meiosis. This is 
substantially the view taken by Lewis (1909). 
There is now abundant evidence that meiosis does not occur 
at corresponding points in the life-history throughout the plant- 
kingdom. All we can say is that it has to occur at some point 
between successive zygoses, and that it always occurs at some break 
in the continuity of vegetative development. Assuming that it 
originally occurred on germination of the zygote, and was thus 
intimately associated with the only break of the kind occurring in 
plants with a simple life-history, it has been shifted, in plants 
with a more complex but regularly periodic life-history, to some 
other point, which varies in different cases, but is generally coinci¬ 
dent with obligate spore-formation. If this be so it is a mistake 
to insist on recognising a “ sporophyte ” which is cytologically 
characterised and is identical throughout the different phyla, 
showing meiosis at spore-formation, and it follows that neither the 
homologous nor the antithetic origin of such a sporophyte can be 
predicated as a universally valid theory. 
We have to recognise two main types of evolution of spore¬ 
bearing phases of the life-history. First the evolution of a post- 
zygotal fruit-body producing spores ( Coleochcete , Floridea, Bryo- 
phyta), secondly, the appearance of a free-living spore-bearing 
alternate generation ( Dictyota , Floridea, Pteridophyta). These 
two phenomena are quite distinct, and may or may not co-exist. 
Meiosis may occur at the formation of the spores of either the first 
(Bryophyta) or of the second ( Dictyota , Pteridophyta) or of neither 
(Coleochcete). It seems better to confine the term sporophyte 
(=spore-bearing plant) to the latter type of phase, and to use some 
such term as post-zygotal sporophase for the former. The natural 
interpretation of their origin is that the “ sporophyte ” in this 
sense is homologous with the sexual plant and that the post-zygotal 
sporophase is antithetic, if it be desired to retain that term for an 
unlike intercalated phase in the life-history. It requires much 
stronger evidence than has ever been brought forward to justify an 
acceptance of the view that these two phases have any direct 
connexion in evolution. A G T 
LITERATURE. 
1 . H. Klebahn. “ Studien iiber Zygoten I.” Jahrb. f. wiss Bot. 22, 1891. 
2. J. Lloyd Williams. “ Studies in the Dictpotaceae.” Annals of Botany, 
Vol. 18, 1904. 
3. C. E. Allen. “ Die Keimung der Zygoten bei ColeocluBte." Ber. deutsch. 
bot. Ges. 23, 1905. 
4. S. Yamanouchi. “ The Life-History of Polysiplionia." Botanical Gazette, 
Vol. 42, 1907. 
5. G. Karsten. “ Die Entwicldung der Zygoten von Spirogyna jugalis, Ktzg.” 
Flora, 91, 1908. 
6 . I. F. Lewis. “ The Life-History of Griffithsia Borneticina." Annals of 
Botany, Vol. 23, 1909. 
7. N. Svedelius. “ Ueber den Generationswechsel bei Delesseria sanguined .” 
Svensk Botanisk Tidskrift. Band 5, 1911. 
8 . I. F. Lewis. “ Alternation of Generations in Certain Florideae” Bot. 
Gaz. 53, 1912. 
