454 The Systematic Value of the New Species. 



b) Fruits thinner, poor in seed; flowers 

 pale yellow, corolla less expanded. 



(Fig. 88, 89) 12. O. albida. 



C. Fruits short and thick, of half the normal 

 size or less. 



a) Flowers erect; seeds small; fruits 



smooth 13. (9. scintillans 



b) Flowers projecting sideways; fruits 



not so stout, poor in seed . . . 14 O. oblonga. 



The characters given in these tables are those which 

 I have myself ordinarily employed in sorting and record- 

 ing my plants. But there are also small differences 

 which practice enables one to recognize with ease, and to 

 emplo}^ with certainty. It is, however, almost impossible 

 to express them in words. And the above mentioned 

 circumstance that the degree of development of all the 

 organs is highly correlated with the individual strength 

 of the plant always makes descriptions appear incom- 

 plete ; but, on the other hand, materially facilitates the 

 discriminations of the living material. 



§ 28. COMPARISON OF THE CHARACTERS OF THE OLD 



AND NEW SPECIES. 



The new species which have arisen in my experi- 

 mental garden from Oenothera Laiuarckiana differ from 

 one another in the same way as do the already known 

 species of the bieiinis-group. I shall now endeavor to 

 prove this important generalization by a detailed com- 

 parison of the two groups. Unfortunately the difficulty 

 of giving this proof is considerably enhanced by the in- 

 completeness of the descriptions which have been given 

 in the literature. The diagnoses are usually short, often 

 based on single herbarium specimens about which we 

 have no means of knowing in what characters they repre- 



