PREFACE 



the evolutionary studies in. the Pteridophyta, this amounted only to a short 'Note on 

 the Cytology of Psilotum with special reference to Vascular Prothalli from Rangitoto 

 Island', which appeared in the Annals of Botany in 1942, since in that case the possible 

 destruction by enemy action of the unique material supplied by the late Dr Holloway 

 of New Zealand, or of the manuscript containing the cytological description of it, 

 would have constituted a serious loss to science. As the war advanced, continuance of 

 the observational work became more and more difficult, and a large programme of 

 genetical inquiry which had been planned to amplify the results for the Male Fern and 

 other species had largely to be abandoned. Many valuable plants were lost either in 

 air raids or from neglect. Nevertheless, at the close of hostihties a sufficient thread of 

 continuity had been maintained to produce the situation that whereas in 1939 some 

 half-dozen draft manuscripts of projected papers had been held back for further work, 

 in 1945 these and several other topics had been developed as far as could reasonably 

 be expected with the material available in England. The congestion which would 

 result from the simultaneous presentation of such a large number of papers to the 

 depleted scientific journals of the immediately post-war years was, however, painfully 

 apparent, and for this reason book form was first envisaged. 



Anyone who has shouldered the task of reducing to manageable proportions the 

 sciendfic notes of fifteen years' observation on more than this number of different 

 topics will perhaps treat the present author with sympathetic forbearance. Without the 

 constant help and encouragement of many friends and colleagues in the University of 

 Manchester and more recently in Leeds, exhaustion might well have set in and the 

 project have been abandoned. Not only has it been a matter of clinching the observa- 

 tions on literally hundreds of the troublesome details which remain uncertain long 

 after the broad outlines of results have been safely established, but the mode of 

 presentation is somewhat unfamiliar. The potential reader of a scientific paper can be 

 judged with reasonable certainty and the style of writing chosen accordingly. The 

 reader of a book is more unpredictable, and whatever modifications of style are adopted 

 to adjust the subject-matter to book form it is almost inevitable that certain parts will 

 be too simple for some readers and too difficult for others. 



To what extent the author will have succeeded in the attempt to write simply is for 

 others to judge, but in the hope of making the work understandable to as wide a circle 

 of readers as possible, most of the essential concepts and such technical terms as are 

 unavoidable are introduced by means of illustrative examples in the first three chapters, 

 and the only mental equipment which is presupposed in the reader is an elementary 

 acquaintance with simple Mendelism and some general awareness as to what is meant 

 by a chromosome. To a botanist who has this equipment as a matter of course a 

 glance at the illustrations will convey the factual content of Chapters 1-3, and the 

 book may be said to begin in earnest at Chapter 4. A zoologist interested in general 

 evolutionary studies, and similarly equipped but lacking an intimate acquaintance 

 with plants, would do well to begin at Chapter 2. A field naturalist, however, whose 

 primary interest is not the laboratory but the life of plants in the field, may need 

 to read parts of the first three chapters twice over, after which he should have no 

 more difficulty in understanding the rest of the book than in reading, for example, 



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