The origin of a land flora : a theory based upon the facts of alternation / by F.O. Bower.

Date:
1908
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Licence: In copyright

Credit: The origin of a land flora : a theory based upon the facts of alternation / by F.O. Bower. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    PREFACE In the year 1874 apogamy was discovered in Ferns by Farlow : and in 1884 instances of apospory in Ferns were demonstrated before the Linnaean Society of London by Druery. These events stimulated a fresh enquiry into the nature and origin of Alternation in Archegoniate Plants. My own observations on apospory confirmed my interest in this question : it seemed to me probable that some biological cause had determined the prevalence and constancy of the alternation, to which apogamy and apospory appear as occasional exceptions. The theory was entertained that the change of conditions involved in the invasion of the Land by organisms originally aquatic had played a prominent part in the establishment of those alternating phases of the life-cycle which are so characteristic of Archegoniate Plants. As early as 1889 I had already written several chapters of a treatise on this subject : but the necessary facts were found to be then so imperfectly known that the work was abandoned, and instead of a full discussion of the matter, the Biological Theory of Antithetic Alternation was briefly stated in a paper published in the Annals of Botany in 1890 (vol. iv. p. 347). The main position of Celakovsky in discriminating between Homologous and Antithetic Alternation was adopted ; but the latter type, as seen in Archegoniate Plants, was recognised as having been fixed and perpetuated in accordance with the adaptation of aquatic organisms to a Land-Habit. The Studies in the Morphology of Spore-producing Members were then entered upon as preliminary investigations to elucidate the facts requisite for a more full statement, and they were published in five parts, from 1894 to 1903. Meanwhile, in 1894 Strasburger contributed to the Meeting of the British Association in Oxford his paper on the “ Periodic Reduction of Chromosomes.” He brought together a wealth of facts establishing the cytological distinction of the alternating generations, and his theoretical position was virtually identical with that of my paper of four years earlier.