60 Elementary Species 



hibit slight but undoubted differentiating fea- 

 tures, and reproduce themselves truly by seed. 

 Descriptions were formerly difficult and so com- 

 plicated that the ablest writers on this genus, 

 Fries and Nageli are said not to have been able 

 to recognize the separate species by the de- 

 scriptions given by each other. Are these 

 types to be considered as elementary species, 

 or only as individual differences? The decis- 

 ion, of course, would depend upon their behav- 

 ior in cultures. Such tests have been made by 

 various experimenters. In the dandelion the 

 bracts of the involucre give the best characters. 

 The inner ones may be linear or linear-lance- 

 olate, with or without appendages below the tip ; 

 the outer ones may be similar and only shorter. 

 or noticeably larger, erect, spreading or even 

 reflexed, and the color of the involucre may be 

 a pure green or glaucous; the leaves may be 

 nearly entire or pinnatifid, or sinuate-dentate, 

 or very deeply runcinate-pinnatifid, or even 

 pinnately divided, the whole plant being more 

 or less glabrous. 



Raunkiaer, who has studied experimentally a 

 dozen types from Denmark, found them con- 

 stant, but observed that some of them have no 

 pollen at all, while in others the pollen, though 

 present, is impotent It does not germinate on 

 the stigma, cannot produce the ordinary tube, 



