69^ 



THE AMERICAN NATUEALIST [Vol. L 



ments this year. However, I obtained from the cross bie7inis X 

 neo-Lamarckiana two distinct classes of plants, (1) a narrow- 

 leaved, smaller-flowered type with heavy pubescence and red 

 papilla} (109 plants), and (2) broad-leaved forms, some larger- 

 flowered, with a much lighter pubescence and few or no red 

 papillae (11 plants). Also, the cross neo-Lamarckiana X biennis 

 (Chicago) gave two clearly defined classes distinguished at a 

 glance by their size and foliage, (1) tall and narrow-leaved (64 

 plants), and (2) shorter and broad-leaved (11 plants). These 

 crosses appear to have given twin hybrids and it should be said 

 that the two groups were recognized and separated when the 

 plants were in the rosette stage and that they consistently pre- 

 sented differences throughout all stages of their development. 

 I shall from time to time make further studies of this behavior 

 with different generations of neo-Lamarckiana. If biennis and 

 biennis (Chicago) are pure species (a matter not yet established) 

 this behavior would indicate that neo-Lamarckiana develops at 

 least two classes of fertile gametes for both pollen and ovules. 

 It thus seems probable that the behavior of neo-Lamarckiana 

 when crossed to other species of (Enothera will parallel that of 

 De Vries's Lamarckiana and thus support the view of several 

 critics of the mutation theory that Lamarckiana, because it gives 

 twin progeny in the F x of certain species crosses, must be itself 

 a hybrid, producing different classes of gametes. 



With respect to the ability of neo-Lamarckiana to throw 

 "mutants" a most interesting situation is presented by its be- 

 havior this summer in the fourth generation. We have noted 

 that a sowing of 764 seed-like structures gave 668 seedlings of 

 which 198 developed as rosettes or mature plants into neo- 

 Lamarckiana. Of the remaining 470 seedlings (668-198) only 

 351 lived to produce rosettes, a much larger group, however, 

 than that containing the parent type, neo-Lamarckiana. We 

 have then in the fourth generation neo-Lamarckiana, an impure 

 or hybrid species, reproducing itself from at least 26 per cent, of 

 its seeds. The exact percentage can not be told, for we do not 

 know whether any plants of neo-Lamarckiana were among the 

 119 seedlings that died. In throwing a large progeny of a type 

 very different from the parent F 3 plant, neo-Lamarckiana in the 

 P 4 exhibited a behavior with strong resemblance to what Bartlett 

 has described as "mass mutation." The types included a num- 

 ber of dwarf forms, but most of the plants resembled franciscana, 



