1920] SHULL— SEEDS 363 



I 



rather wide application, and deserve to be considered by those 

 interested in the problems of absorption. While on the theoretical 

 side certain features of the work have been disappointing, it will 

 be worth while to give a somewhat detailed account of the experi- 

 ments, as a contribution to our knowledge of the facts concerning 

 the intake of water by dry organized matter. 



I wish to acknowledge my indebtedness to Professor S. P. 

 Shull for valuable assistance with the mathematical part of the 

 work. He has given generously of his time during the. last five 

 years to a painstaking analysis of the data, which has made possible 

 a degree of accuracy otherwise unobtainable, and without which 

 the general significance of the data could not have been fully 

 appreciated. He has also tested many hypo theses as to the influ- 

 ence of factors upon intake rates. The principal part of the 

 experimental work was done in the Laboratory of Plant Physiology 

 at the University of Kansas, and part of it at the University of 

 Chicago during the summer of 1914. The privileges of the Hull 

 Botanical Laboratory for this work were much appreciated. 



Materials and methods 



The experiments were carried on with the lower seeds of 

 Xanthium pennsylvanicum Wallr., and the naked cotyledons of 

 several varieties of peas, the Canada green field pea, the Tom 

 Thumb garden pea, and the Small Scotch Yellow pea of commerce. 

 The cockleburs were chosen for their semipermeable coats, and 

 the peas because the elimination of coat effects is easy. At first 

 seeds of Xanthium were collected in the field; but these were soon 

 replaced by pure line seeds grown on the breeding grounds of the 

 University of Kansas in 1913. It was felt that such seeds might 

 be more valuable than those of mixed genetic origin, more uniform 

 in behavior, and the absorption data therefore more susceptibly 

 to mathematical consideration. After it had become evident that 



* 



age, environmental history, genetic origin, and other factors might 

 influence the intake phenomena, seeds were obtained from plants 

 growing near the writer's home in Lawrence, Kansas. Slight 

 differences in the shape and appearance of the seeds of different 

 plants indicated possible lack of genetic purity, although the 



