FOREWORD 



It is an honor to be asked to contribute a foreword to this stimulating 

 pubHcation. The book, of course, owes its inception to Dr. Verdoorn's 

 enthusiastic interest in the documentation of plant science. As a matter of 

 history, it is the last of a series of titles which were originally announced 

 by him before the war and have one by one been published during the last 

 seven years. The authors of these chapters have cooperated generously 

 and have produced conscientious and thorough reviews of their several 

 fields. They are authoritative and familiar with the ramifications of the 

 work they discuss. One of them is himself the author of a book in the 

 same general field.^ At the moment, therefore, these comprise almost the 

 last word. 



Nevertheless, although the present seems a particularly opportune 

 moment for the appearance of this book, there can be no doubt that in this 

 field, which is developing so rapidly, fundamental changes in outlook might 

 well come at any moment. Such a highly flexible situation is of course 

 typical of experimental plant science, which in many respects is still some- 

 what embryonic, but it is perhaps particularly so of the branches of plant 

 physiology and agronomy which are discussed here. 



The reasons for this are basically simple. The physiology of flowering, 

 with which this book deals, has as yet no basis in the general physiology and 

 biochemistry of the plant. The fundamental discoveries on which it rests 

 are the effects of the chilling of germinating seeds, and of the varying of 

 the length of day in mature plants approaching the stage of "readiness to 

 flower (Bltihreife)". Both of these are essentially ad hoc discoveries which 

 did not arise directly from a continuing chain of closely-knit research and 

 deduction, such as, for instance, that on which genetics rests today, or even 

 that which led to our rather extensive knowledge of the auxins. They have 

 inspired a large amount of experiment and have led to very important 

 practical applications in the agriculture of both temperate and tropical zones, 

 which are discussed in the several chapters of this book. But the under- 

 lying problems are difficult to attack and, indeed, it is not quite clear that 

 they can even be formulated. What, for instance, is the nature of the 

 change from the vegetative to the flowering state? Is it localized in the 

 buds themselves, as would be implied by the concept of a flowering hormone, 

 of which the buds would be the receptors, or is it systemic — a symptom 

 of an inner complete change in metabolism, as in the theory of phasic 

 development? Curiously enough, these two viewpoints have each become 

 associated with one of the two main fields of endeavor, namely photoperiod- 

 ism and vernalization respectively. 



Only recently have these two basic ideas shown signs of approaching 

 one another. It should be pointed out that the demonstration by Gregory 



^Whyte, R. O., Crop Production and Environment (London: Faber & Faber), 

 1946, 372 p. For the sake of completeness the following recent book may also be 

 mentioned: David, R., Facteurs de developpement et printanisation des vegetaux 

 cultives (Paris: Hermann et Cie.), 1946, 177 p. 



