86 Relationships of Bryophyta to other Phyla. 
of the Vascular Plants. It has been suggested that the Authoceros 
type of sporogonium forms a practicable starting point for the 
evolution of the Pteridophyta, but there are very great difficulties 
in the way of accepting such a hypothesis, which postulates the 
origin of roots and leaves from a sporogonium in the face of the 
fact that no known Bryophyte shows the slightest tendency to the 
development of such organs—unless, indeed, we may regard the 
foot of the typical Bryophyte sporogonium as a potential root, and 
the apophysis of Mosses like Polytrichum as a potential leaf. 
If we adopt the view that the sporophyte generation originated 
as a free-living thallus, which later became hemmed in and retained 
in the parent plant, we are at once freed from these difficulties. 
However, it appears to the writer that the balance of evidence is 
distinctly in favour of the view that the Bryophyte sporogonium 
had an antithetic origin. In the general “ pedigree table ” on p. 40 
indicating the writer’s general conclusions regarding the inter¬ 
relationships between the main groups of Bryophyta, expression is 
given to the suggestion made by Mr. Tansley that the “ Archegoniate 
Algae ” from which the primitive Bryophytes arose also gave rise to 
the primitive Pteridophytes, because this appears preferable to the 
view that the Pteridophytes arose from the Anthocerotales or other 
highly differentiated Bryophytes. 
The following list of literature merely indicates a few of the 
more important books and papers dealing with the subject; 
references will be found in these to other sources. 
LITERATURE. 
1. Bower, F. O. “ On Antithetic as Distinct from Homologous Alternation 
of Generations.” Ann. of Bot., 1890. 
2. ,, “ The Origin of a Land Flora.” London, 1908. 
3. Braun, A. “ Gymnospermie der Cycadeen.” Ber. d. k. Adad zu. Berlin, 
1875. 
4. Celakovsky, L. “ Ueber die verschiedenen Formen und die Bedentung 
des Generationswechsels der Pflanzen.” Sitzungsb. 
d. ges. d. wiss. Prag., 1874. 
5. Discussion on “Alternation of Generations” at the Linnean Society. 
New Phytologist, VIII, p. 104, 1909. 
6. Lang, W. H. “A Theory of Alternation of Generations in Archegoniate 
Plants based upon the Ontogeny. ’ ’ N eyv Phytologi st, 
VIII, p. 1, 1909. 
7. Pringsheim, N. “ Sprossung der Moosfruchte und den Generations- 
wechsel der Thallophyten.” Jahrb. f. wiss. Bot., 
Band XI, 1878. 
8. Scott, D. H. Presidential Address to Section K of the British Association 
at Liverpool, 1896. 
9. Tansley, A. G. “ Lectures on the Evolution of the Filicinean Vascular 
System. I. The Origin of the Pteridophyta.’ 
Cambridge, 1908. 
10. ,, “Professor Bower on the Theory of Antithetic Alternation 
of Generations.” New Phytologist, VII, n. 117. 
1908. 
