152 



BRADLEY MOORE DAVIS 



3. Inflorescence. The close inflorescence (fig. 4) has sessile bracts, broad at the 

 base, early in the season equalling or exceeding the length of the young buds; later 

 in the season the bracts may be much shorter. 



4. Buds. The buds in the largest-flowered forms of Lamarckiana (fig. 4) are 

 8 to 9 cm. long. The cone is stout and 4-angled. The sepals are green, in some 

 forms streaked with red; sepal tips thick or not markedly attenuate. The pubes- 

 cence on sepals, a heavy pilose and puberulent covering, consists of long hairs 

 arising from papillae among numerous short sessile hairs. In the smaller-flowered 

 forms the buds are from 7 to 8 cm. long and correspondingly smaller in their parts. 



5. Floivers. The largest-flowered forms have petals 4 to 4. 5cm. long, and stigma 

 lobes 5 to 7 mm. above the tips of the anthers. The smaller-flowered forms have 

 petals 2.5 to 3 cm. long and frequently the stigma lobes are about on a level with 

 the tips of the anthers. The ovaries bear red papillae at the base of long hairs. 



6. Capsules. The capsules vary in shape, in some forms being stout and rela- 

 tively short, about 2 cm. long; in other forms more attenuate and about 3 cm. 

 long. 



Some remarks will not be out of place on the reason why the 

 problem of the origin of Oenothera Lamarckiana is a matter of 

 such great interest. As is well known the e\ddence for the muta- 

 tion theor}^ of De Vries rests chiefly upon the behavior of Lam- 

 arckiana in throwing off marked variants ("mutants") in suc- 

 cessive generations. De Vries assumed that Lamarckiana was 

 a native American species and interpreted its beha\'ior as the gi\"ing 

 rise to new species through the sudden appearance of wide varia- 

 tions (saltations). Many botanists are critical of the interpre- 

 tation of De Vries and hold that Lamarckina is not representative 

 of a wild species but is, on the contrary, of hybrid origin, and that 

 its beha\'ior illustrates the phenomenon of the splitting of a hybrid 

 into diverse forms. So far no clear evidence has been presented 

 that Lamarckiana is or ever was the component, as a wild species, 

 of any native flora, but it is onlj^ fair to state that the southern 

 and western United States have not been thoroughly explored. 

 This is why we hope that botanists of these regions will push 

 the search with vigor. 



For the view that Lamarckiana is hybrid in character there is 

 evidence from experimental studies upon the plant itself, the lat- 

 est and best of which are described in a recent paper of Heribert- 

 Nilsson.' There are also the experimental studies of the writer^ 



^ Heribert-Nilsson, N., Die Variabilitat der Oe7iolhera Lamarckiana nnd das 

 Problem der Mutation. Zeitsch. ind. Abstam. u. Vererbungslehre, 8: 89, 1912. 

 » See Davis, Am. Nat. 46: 193, 1911, and 46: 377, 1912. 



