THE PI. ANT WORI.D 231 



direction, you may feel warranted in addressing any botanist and asking 

 for help. I do not wish to be understood as saying that original research 

 can easily be done by any one. What I do assert, however, is this. An 

 intelligent teacher, who can teach, ought to be capable of giving himself 

 training by prosecuting a thorough study of a particular subject. Every 

 careful bit of work done will lead him to and prepare him for the next. 

 Power increases with accomplishment. Small successes stimulate to 

 greater ones. Even if time and strength are too limited to allow deep 

 penetration into a problem, individual initiative and power may be de- 

 veloped, and these qualities make the teacher to experience that mental 

 elasticity which is a prime factor in the successful teacher. 



The question of the origin of species has during the post-Darwinian 

 period of discussion become clouded. The real basis of scientific thought 

 has been partially lost sight of, namely, experimental observation upon 

 the living organism. Very little new light comes by the way of academic 

 discussion and analysis. If we are to gain more knowledge of organic 

 nature we must find out by inductive methods what is actually going on. 

 Part of the great value of the work of Professor de Vries lies in this 

 that it has again sounded loudly the principle that the ' ' test of doctrine ' ' 

 is experiment. Professor de Vries has made a beginning full of promise ; 

 that he has set a pace hard to follow need not be said. Nevertheless, 

 there are many who, with a word of guidance and suggestion, may be 

 well able to play a small, perhaps, but yet worthy part in the solution of 

 the problems of plant evolution. It is with great pleasure, therefore, that 

 we print the following lines written by Professor de Vries for The 

 Plant World to the teachers of this country, 



THE METHOD OF EXPERIMENTATION UPON THE ORIGIN 



OF SPECIES. 



BY HUGO DE VRIES. 



Tlie origin of species has to become an object of experimeutal investigatiou. In 

 the first place the polymorphy of our ordinary wild plants has to be studied, and the 

 single types, which are met with in field observations, have to be tested by sowing ex- 

 periments during two or more generations in the garden. If the flowers are protected 

 against the visits of insects, which may be done by enveloping the inflorescences or 

 the single flowers in paper bags, bound with a thread around the stem below the flower ; 

 and if the seeds are gathered and sown separately for each single individual — which is 

 the great principle — the progeny will prove uniform and constant in most of the in- 

 stances. It is, however, necessary to ascertain the fact in each single case, and to 

 discover all those cases which behave otherwise, and which may become the starting 

 points for long series of new discoveries. Such work does not require vast laboratories 

 or rich installations, and I desire especially to emphasize that all friends of nature are 

 earnestly requested to take part in the work. Hundreds of species have to be tried, in 

 order to prove the general rule and to find out the exceptions. Assiduity and correct- 



