New Species of Oenothera 535 



The leaves are narrow, and a curious feature 

 of this species is the great brittleness of the 

 leaves and stems, especially on annual individ- 

 uals, for example, on those that make their 

 stem and flowers in the first year. High tur- 

 gidity and weak development of the mechanical 

 and supporting tissues are the anatomical cause 

 of this deficiency, the bast-fibers showing thin- 

 ner walls than those of the parent-type under 

 the microscope. Young stems of rubrinervis 

 may be broken off by a sharp stroke, and 

 show a smooth rupture across all the tissues, 

 while those of Lamarckiana are very tough and 

 strong. 



Both the giant and the red-veined species are 

 easily recognized in the rosette-stage. The very 

 young seedlings of the latter are not clearly dif- 

 ferentiated from the Lamarckiana, and often a 

 dozen leaves are required, before the difference 

 may be seen. Under ordinary circumstances 

 the young plants must reach an age of 

 about two months before it is possible to 

 discern their characters, or at least before 

 these characters have become reliable enough 

 to enable us to judge of each individual 

 without doubt. But the divergencies rapidly 

 become greater. The leaves of 0. gigas are 

 broader, of a deeper green, the blade more 

 sharply set off against the stalk, the whole ro- 



