22 



find an object suited to exact quantitative worklng; the 

 same motive has restrained me from extending my inves- 

 tigation to other plants. Besides, an exhaustive study of 

 one object is worth more than a superficial investigation 

 of many plants, and the time available was not sufficient 

 for an exhaustive investigation of more than one object. 



Ail seedlings used were from the same lot of oats, bought 

 at W. C. Verbeek's in Utrecht in October 1909. Probably 

 it would hâve been better had I used a pure strain, but 

 this only occurred to me after I had already started m y 

 experiments, and so it wàs, too late to adopt this précaution. 

 The coleoptiles of Avena are especially well fitted forgeo- 

 tropic investigations, as has been remarked again and again. 

 The simple shape of the coleoptile makes it possible to 

 observe the first beginning of the reaction very accurately. 

 For ail anatomical particulars I refer to Rothert'); 

 Blaauw^) gave a description of the method of growing 

 the seedlings, which I hâve follov^ed with but few altérations. 



As I did not invariably succeed quite well in growing 

 a quantity of seedlings sufficient for my experiments, I 

 wish to describe in détail the method, which yielded the 

 best results. For further particulars concerning the object 

 of experiment I refer to § 7, where ail peculiarities of the 

 Avena-coleoptiles will be mentioned again in discussing 

 the sources of error. 



The husked oat-grains were soaked by El a au w^) in 

 water in earthen ware dishes, by Mrs. Rutten-Pekel- 

 haring^) on moist saw-dust. I was much more satisfied 

 with the method, used by P r i n g s h e i m 0, of soaking 



1) W. Rothert, 1894. 



2) A. H. B 1 a,a u w, 1909. 



3) A. H. Blaauw, 1909, p. 11. 



4) C. J. R u 1 1 e n-P e k e 1 h a r i n g, 1910, p. 254. 



5) E. Pringsheim Jr., 1909. 



