6o 



STUDIES IN SEEDS AND FRUITS 



as one follows the trend of still more recent investigations. 

 However, I pass over for a time the results of the brilliant 

 researches of Paul Becquerel, carried out in the laboratory of 

 the Sorbonne between 1904 and 1907, because in as far as 

 they deal with matters discussed in these pages they are 

 primarily concerned with the impermeability of seeds to air, 

 and will be more appropriately referred to in the chapter on 

 the hygroscopicity of seeds. 



In following the history of the investigation of this subject 

 from the data at my disposal, the next advance on solid ground 

 seems to be that supplied by the results obtained by Mr 

 Crocker. If Dr Gola opened our eyes as to the frequency 

 of impermeability in the seed-world, Mr. Crocker has done 

 much to enlighten us as to its biological significance. In 

 different papers published in the Botanical Gazette (Uni- 

 versity of Chicago Press, 1906-9) he expresses the opinion 

 that " delayed germination," or, as we might term it, " seed- 

 longevity," is more generally due to seed -coat characters 

 "limiting or entirely excluding water or oxygen - supply " 

 than to embryo characters or the "so-called dormancy of 

 protoplasm." His results go far to establish the view put 

 forward by Nobbe and Hanlein in 1877, and quoted by 

 him, that " delayed germination is due in many cases to 

 the impermeability of the seed-coat to water." One of his 

 papers (" Role of Seed-coats in Delayed Germination," October 

 1906) is concerned especially with this point ; but he repeats 

 the general conclusion formed, as above given, in a later paper 

 ("Germination of Seeds of Water-plants," November 1907), 

 and in a short article in the same publication in January 1909. 

 It may be remarked before concluding this reference that Mr 

 Crocker regards impermeability to water as much more con- 

 ducive to seed-longevity than imperviousness to oxygen {thid.^ 

 October 1906) ; and this is the point that is of most interest to 

 us in the present stage of this discussion. " The coats that 

 exclude water " (he writes) " are undoubtedly much better 

 adapted to securing a long delay." 



