26 



DE. E. E. GATES— CONTEIBUTION TO A 



short, so fhat nearly all the flowers were self-pollinated, and the petals were partly 



cruciate and partly normal on the same plant. Measurements showed ovary 11 mm. ; 



hypantliium 35 mm.; hud-cone 20 mm.; free sepal tips 6 mm,; petals 30 mm. long; 



cruciate petals 7 mm. hroad ; normal petals 32 mm. broad ; hypantliium very stout, 

 3' 5 mm. in diameter. 



In my cultures 737 plants of DeYries's race of O. Lamar chiana have been grown 

 from pedigree seed. Of the larger cultures, 170 plants in 1907 gave one mutant 

 O. rubrinei^vis , and 115 plants in 1909 gave two O. lata mutants. The remaining plants 

 were in small cultures not exceeding 50 plants of each pedigree, and they produced no 



mutants. 



0. laevifolia. 



This species has never appeared as a mutant from 0. Lamarckiana, but was found by 

 DeVries in the locality at Hilversum from which his cultures of 0. LamarcMana were 

 obtained. I have already referred to some of the differences from 0. Lamarc'kiana, 

 The leaves both of the adult rosette and the stem are distinctly narrower than in 

 O. LamarcMana^ as seen from PI. 2. figs. 16, 17, and 18; the latter, which shows the 

 range of variation in width and amount of crinkling in the leaves of the adult rosettes, is 

 instructive for comparison with 0. Lamarckiana (PL 1. fig. 6). PI. 1. fig, 13 and 

 PI. 2. fig. 14 again show clearly the three types of leaves which appear in the develop- 

 ment of a rosette. These are photographs of the same plant, taken with an interval 

 of 8 days. Pig. 16 also exhibits the three leaf types. It must be said that photographs 

 are frequently rather inadequate to represent the differences between related forms to 

 those unfamiliar with the characters, yet it is hoped that a careful comparison of figs. 5 

 and 17, of 6 and 18, of 8 and 19, will give a true conception of some of the main diff'er- 

 ences between 0. Lamarckiana and 0. laevifolia. The stem-leaves of the latter are more 

 or less furrow-shaped, and stand out stifilyfrom the stem. Eora systematic enumeration 



1 



of the characters, reference may be made to DeYries (1909, i. p. 309) or Gates (1909 c). 



PI. 2. fig. 20 shows the fruiting stage of a typical individual. Comparison with PI. 3. 

 fig. 31 for O. rubricalyx shows that the bracts are much narrower and shorter than in that 

 form. Incidentally it may be observed in fig. 20 that late in the season the stis^ma 



sometimes pushes out of the bud and expands before the latter opens. As is well- 

 known, the flowers of all the Oenotheras decrease rapidly in size towards the end of the 

 season. But the decrease is not always in the same proportion in all parts of the flower. 

 When the diminution in length of petals and sepals is more rapid than in length of 

 style, the stigma will protrude from the unopened bud. This is not an uncommon con- 

 dition in all the large-flowered Oenotheras late in the flowering period, and it of course 

 increases the probability of crossing. But flowers which develop so late in the season 

 have a very poor chance of maturing seed, and it is not believed that such a phenomenon 

 has any adaptive significance in securing occasional cross-fertilization in the race. Crosses 

 with other individuals are secured, in the large-flowered Oenotheras in America, through 

 the visits of moths in the evening when the flowers open. The fact that part of the species 

 composing the Onacjra group are strictly self-pollinating while part are open-pollinated, 



