266 



SUMMARY OF RESULTS 



[CII. 



for Archegoniate Plants. The argument based on comparison with the 

 Phaeophyceae was first stated in 1903 by B. M. Davis {Ann. of Bot. XVII, 

 p. 477; see also Schenck, Englers Jahrb. 1908, Bd. XLII, p. i), and illus- 

 trated by diagrams here quoted as Fig. 755. His suggestion that the anthe- 

 ridium and the archegonium represent derivatives from a common source 

 received support from Holferty's demonstration of bi-sexual archegonia in 

 certain Mosses (Vol. I, Fig. 280): and more recently by the discovery of in- 

 determinate sex-organs in Lycopodium hiciduliun by Spessart {Bot. Gas. 1923, 

 Vol. LXXiv, PI. XVI, Figs. 60,61). Exceptional states observed by Miss Lyon 



Fig- 755- Diagrams illustrating the possible evolution of the archegonium and antheridium 

 from the plurilocular sporangium. a = pIurilocular sporangia with large and small 

 gametes discharged from the apex, after the habit found in certain Phaeophyceae (e.g. 

 ChilionetJia Nathaliae, Ectocarpiis virescens, etc.). /; = plurilocular gametangia of a 

 hypothetical algal type, which has adopted a terrestrial habit. The outer layer of gamete- 

 mother-cells has become sterilised as a protective capsule enclosing the fertile tissue. 

 The gametes are differentiated in sex, but both are still motile. d= plurilocular game- 

 tangia of somewhat higher hypothetical forms, at the level of heterogamy. Sterilisation 

 has proceeded so far in the female gametangium that only a few gametes are matured 

 at the base of the organ, and these are eggs. «'= simple types of archegonium and 

 antheridium : the female gametes are reduced to one, while the number of male gametes 

 is greatly increased, and these cells are smaller and more highly specialised than in the 

 earlier conditions. (After B. M. Davis. ) 



and others also accord with the view that the sex-organs of the Arche- 

 goniatae are differentiated gametangia {Bot. Gas. 1904, Vol. XXXVII, p. 280). 

 There is then reason for recognising in the propagative organs of both 

 generations a parallel progression in sexual differentiation ; but apparently 

 that in the gametangia preceded by long ages that in the sporangia. This 

 parallel gives added interest to the comparison between the antheridia and 

 sporangia of Ferns in respect of bulk, which may in the future take an 

 important place in their phyletic comparison (Vol. I, p. 290). 



It may still remain an open.question whether the nearest points of phyletic 

 contact of the Algae with the Archegoniatae are to be found in the Red, 

 the Brown, or the Green Algae: analogies may be traced with each of these. 

 But whatever real relationship there may have been, indications of it should 



