& 



368 SUMMARY OF CURRENT RESEARCHES RELATING TO 



change from the extruded ovum to the fertilised egg which is 

 retained within the parental body and is submitted to the physio- 

 logical influence of the maternal tissues — a change which probably 

 coincided with or resulted from the change to a terrestrial life 

 — opened up possibilities for profound changes and developments, 

 resulting in the difference in body form between sporophyte and 

 gametophyte. The Bryophyta and Pteridophyta may have had quite 

 independent origin from different sets of organisms at the same or at 

 different geological periods. Indeed, the main groups of the Pterido- 

 phyta, such as Lycopodiales and Filicales, may have started on different 

 lines. The dispersal of the plant is assumed to have been insured by 

 the free shedding of air-borne spores. The two generations in each 

 species are regarded as homologous. The number of chromosomes and 

 the mode of reproduction are assumed to have been different in the two 

 generations of the ancestral forms. The further evolution of the 

 organisms would have involved the occurrence of variation and selec- 

 tion. The consequent changes may have been manifested in either or 

 both generations, depending on the conditions. The sporophyte may 

 have advanced while the corresponding gametophyte remained un- 

 altered. The author briefly applies his hypothesis to the three great 

 groups — Ferns, Lycopods, Equisetaceaa. 



Alternation of Generations.* — W. H. Lang's exposition of his 

 ontogenetic theory of the alternation of generations before the Linnean 

 Society, on February 18 th, is reported almost verbatim, together with 

 the criticisms offered by F. 0. Bower, D. H. Scott, J. B. Farmer, F. W. 

 Oliver, and A. (x. Tansley. 



Water-cavities of Equisetum.t — J. H. Schaffner contributes a note 

 upon a condition noticed during winter in Equisetum hyemale. The 

 vallecular, carina!, and central cavities were found to be filled with ice. 

 Portions of the plants were taken indoors and placed under observation, 

 when it was found that the water which resulted from melting the ice, 

 disappeared more or less rapidly in proportion to the size of portion of 

 stem, those including a portion of the rhizome retaining the water for 

 the longest period. Observations made in May upon other species of 

 Equisetum showed no free water in any of the cavities. The water 

 present during winter appears to have some physiological connection 

 with the plant in relation to extreme cold. 



Ferns of the Vosges.J — E. Walter ca^ls attention to the occurrence 

 of Aspidium aculeatum in the Vosges Mountains, points out the 

 characters which separate it from A. lobatum, and sketches out the 

 geographical distribution of the two species. 



The same author § gives an account of the ferns on the sandstone in 

 the neighbourhood of Zabern in the Yosges. Several ferns of southern 



* New Phytologist, viii. (1909) pp. 104- 16. 



t Ohio Nat., ix. (1908) pp. 393-4. 



1 Mitt. Pkilom. Gesell. Elsass-Lothringen, iii. (1907) pp. 455-60 (pi.). 



§ Tom. cit., pp. 547-81 (figs.). 



