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The Controlling Influence of Carbon Dioxide in the Maturation, 

 Dormancy, and Germination of Seeds. — Part I. 

 By Franklin Kidd, B.A., Fellow of St. John's College, Cambridge. 



(Communicated by Dr. F. F. Blackman, F.B.S. Beceived January 10,— 

 Bead March 5, 1914.) 



Introduction. 



The cause or causes conditioning arrested development in moist seeds and 

 the nature of the impetus which results in germination are still in most 

 respects obscure. The problem of the non-germination of maturing seeds 

 while still upon the parent plant and the large range of cases of delayed or 

 non-germination of shed seeds which to all appearances are in good condi- 

 tions for germination form the basis of this research. 



It is to be emphasised that the problem of seed dormancy is not limited 

 to the case of the dry seed. The more important, but less obvious, condi- 

 tions of dormancy are those found in moist maturing seeds, and in cases of 

 delayed germination in the presence of sufficient conditions of moisture and 

 temperature. It is these which have the most interesting analogies in other 

 fields, and an analysis of which may be more fruitful from the point of view 

 of physiology in general. 



It is useful at the outset to examine certain conclusions that are being 

 reached by workers who have set themselves to elucidate the processes of 

 similar phenomena in other departments of physiology. In certain aspects, 

 the latency of the unfertilised ovum offers an analogy with the latency of 

 moist seeds. In each case the latency is only ended by the onset of definite 

 causes ; in each case in the absence of these causes the period of latency is 

 sooner or later terminated by death ; and in each case also the sequence of 

 changes that follow the onset of the stimulus is, in a broad sense, physio- 

 logically comparable. The interest of this analogy, moreover, is increased 

 by the prominence which has recently been given to a simple interpretation 

 of the nature of the fertilisation stimulus. Loeb (1) has attempted to 

 outline its essential features as follows. These appear to be, firstly, an 

 acceleration of oxidations which follows destruction by cytolytic agents of 

 a cortical layer in the egg which has hitherto prevented oxygen from 

 reaching the surface of the egg and from penetrating into the latter 

 sufficiently rapidly. Secondly, Loeb believes that an internal change takes 

 place which renders innocuous the toxic products of oxidation. He shows 

 that the unfertilised matured egg dies soon, and he attributes this to the 



