174 



Davis. 



Oenothera biennis L, 



Cotyledons'). 6 — 7 mm. long, broad at the 



base and tapering to a rounded point 



(Fig. 1, biennis). 

 Young rosettes. A close cluster of sliort- 



petioled, broadly-elliptical or ovate leaves 



(Fig. 2, biennis). 



Oenothera muricata L. 



Cotyledons'). About 5 mm. long, broadly 



elliptical, cut away at the base (Fig. 1, 



muricata). 

 Young rosettes. A loose cluster of long 



petioled, narrow-elliptical or spatulate 



leaves (Fig. 2, muricata). 



Fig. 5. Rosette of muricata from a biennial plant, exhibiting the extreme development 

 of long, narrow leaves. Contrast with Fig. 3, biennis. 



Mature rosettes'), 'do — 4 dm. broad. A Miiture rosettes-). 3— 3'5 dm. broad. A 



close cluster of broadly-elliptical leaves 

 tapering to relatively short petioles, 

 crinkled (Fig. 3). Rosettes of biennial 

 plants develop much larger and broader 

 leaves. 



looser cluster of narrow-elliptical leaves 

 taperiug to relatively long petioles, plane 

 (Fig. 4). Rosettes of biennial plants devel- 

 op much longer and relatively narrower 

 leaves (Fig. 5). 



') The cotyledons are measured on the appearance of the first leaf as a small 

 triangular structure. 



') Rosettes are considered as "mature" when they begin to send up their central 

 shoots. 



