PEIZE-QUESTIONS OF SCIENTIFIC SOCIETIES. 441 



author will support his opinion by his own researches and compare 

 them with those of other experimenters. 



XIII. The progress of science has brought some sort of confusion in 

 the determination of several species of plants and even in the definition 

 of the species. It is observed that most of the species formerly recog- 

 nized include diverse forms which some call races or varieties, and oth- 

 ers species. The works already written in regard to Rubus, Sieracium, 

 Mentha, 'Salix, &c., are important, but they have the fault of being con- 

 fined to species very closely related to each other, consequently very ■ 

 confused. Besides, the forms studied have usually been confined to 

 those of a certain country, as the Buhus of England or Germany, in- 

 stead of comparing all the forms of a certain species of Euhus. Conse- 

 quently, there is required a profound study of some of Linnseus's species, 

 selected from those which present more or less diverse forms, paying 

 particular attention to the following particulars : 



First. The species should be wild plants, atleast ten and at most twenty 

 in number, belonging to at least two natural families, and growing in 

 well-explored countries, such as Europe, the United States, &c. 



Secondly. The author should endeavor to describe and classify all the 

 forms which are more or less distinct and more or less hereditary that 

 enter into the Linnieau species, taking care to specify their place of 

 growth, their rank, and to tell if the observations were made from living 

 l)lants, from dried specimens, or if they are described from books. 



Thirdly. Their mode of fecUndatioi/ should be examined, and the point 

 to which certain forms may be attributed to crossing determined. 



Fourthly, The amount of hereditary influence on forms should be de- 

 termined by experiment, at least in a certain number of cases, and in 

 the case of woody species during at least two generations. 



Fiithly. For woody species it will be necessary to determine the pos- 

 sibility or impossibility of grafting on each other forms belonging to 

 the same kind. 



Sixthly. The classification of forms in species, races, or subspecies, 

 varieties, subvarieties, variations, sub variations, and other subdivisions 

 which may be necessary, should be based at the same time on exterior 

 forms and on the closest affinities shown by fecundation and grafting. 



Januaey 1, 1878. 



Our knowledge is still more limited in regard to the quantity of mud 

 and other material brought by rivers to the Netherlands, the places where 

 these matters are most frequently deposited, and the circumstances 

 which influence their transport and their deposit. We wish to see these 

 points cleared up for one or several of the rivers of our country, through 

 observations or experiments continued during many years. 



The society recommends contestants to omit in their pajjers every- 

 thing which has not an immediate connection with the question pro- 

 posed. The society desires to find clearness and precision in everything 



