The Laws of Mutatioii. 251 



field contains no more than some thousands of plants, 

 that is to say not much more than could be supplied by 

 the seeds of a single individual. The seeds which do 

 not produce adult plants either do not germinate or the 

 seedlings which come up die young. Yet in spite of the 

 severity of the competition, O. laevifolia and O. hrcvi- 

 stylis have maintained themselves for more than twelve 

 years. -^ 



III. Most of the new forms that have appeared are 

 elementary species, and not varieties in the strict sense 

 of the term. Elementary species are distinguished from 

 their nearest allies by nearly if not quite all their char- 

 acters. The differences are often so slight as to escape 

 notice by an eye not trained to observe them ; and they 

 are particularly apt, as systematists so often complain, 

 to become lost in dried specimens. This latter is how- 

 ever fortunately not the case with the new forms whose 

 origin I have witnessed ; for they are distinguishable 

 from one another and from O. Lamarckiana as herbarium 

 specimens far more easily than, for example, specimens 

 of this last species are from O. biennis. 



This close familiarity with each form can only be 

 attained by a careful and minute study and description 

 of all the organs of the plant at every stage of its devel- 

 opment. Once a plant is thoroughly known in this way 

 it can be recognized at almost any stage. 



Varieties are distinguished from the mother species 

 usually by one single character or at most by two or 

 three, whilst they resemble them in all others. Apart 

 from this point, the difference between species and vari- 

 eties is to a large extent arbitrary, since when tested ex- 

 perimentally the one is just as constant as the other. 



*And afterwards until now (Note of 1908). 



