May 9, 1902.] 



SCIENCE. 



723 



branches are placed at a sharp angle with 

 the erect stem and in their turn bear nu- 

 merous side branches. Nearly all branches 

 and side branches are crowned with flowers, 

 which, because of their size and bright 

 yellow color, attract immediate attention, 

 even from a distance. The .flowers, as the 

 name indicates, open towards evening, 

 shortly before sunset, and this so suddenly 

 that it seems as if a magic wand had 

 touched the land and covered it with a 

 golden sheet. Bumble bees and moths, 

 especially those of Plusia gamma and of 

 Agi-otis segetum, are the principal visitors. 

 During the hot weather the flowering 

 period is limited to the evening hours. In 

 daytime often nothing is to be seen but 

 faded and half-faded flowers and closed 

 buds. Each flower bears a long style with 

 four or more stigmas, which protrude at 

 some distance above the eight anthers, and 

 would therefore, as a rule, not be fertilized 

 without the help of insects. When the 

 flowers, including their apparent stem, the 

 calyx tube, drop off, there remains behind 

 a perigynous ovary, which finally becomes 

 a capsule. At first green, it becomes brown 

 on ripening and finally opens with four 

 valves, setting free the seeds. A stem with 

 ten to twenty, or even thirty or forty, cap- 

 sules is not rare, nor consequently a plant 

 with a hundred or more fruits. And since 

 each fruit contains more than a hundred 

 seeds it would be quite possible for a plant 

 of this species to reproduce itself several 

 thousandfold, provided all seeds could ger- 

 minate and grow. 



It is this plant, Oenothera Lamarchiana, 

 which exhibits the long-sought peeuliai-ity 

 of producing each year a number of new 

 species, and this not only in my experi- 

 mental garden, but also when growing wild. 

 But in the latter case the new species have 

 as a rule but a very short lease of life ; they 

 are too weak and too few in number to sur- 

 vive in the struggle for existence with the 



hundreds and thousands of their fellows. 

 In the experimental garden, however, they 

 can be recognized at an early stage, and 

 with especial care may be isolated and cul- 

 tivated. It is thus that in the experi- 

 mental garden we are readily able to see 

 that which, among wild-gi'o-vving plants, is 

 lost to observation. 



The new species vary but little from the 

 old. An inexperienced eye detects no dif- 

 ference. Only a careful comparison shows 

 that here we have to deal vdth a new type. 

 There are some, for instance a dwarf 

 species, and species with a peculiar close 

 crown (0. nanella and 0. lata), which at 

 once attract our attention, because they are 

 short of stature. Again, some are more 

 slender and delicate, others low and un- 

 branched, or robust and tall. A difference 

 may be detected in the shape of the leaves, 

 their color and their surface. The fruits 

 vary in the same manner; sometimes they 

 are long, sometimes short, sometimes 

 slender, sometimes stout. The more one 

 observes these plants, the more differences 

 one sees. Gradually it becomes apparent 

 that here we have to deal, not with a chaos 

 of new forms, but rather with a series of 

 sharply defined types. Each of these types 

 originated from a seed produced by the 

 parent species, growing wild, and fertil- 

 ized in the usual manner, or growing in 

 the experimental garden, and fertilized 

 artificially, with its own pollen. 



Here then we have our first result. The 

 new species originate suddenly, without 

 preparation or intermediate forms. But 

 they do not differ from the old species like 

 an apple from a pear, a pine from a spruce, 

 or a horse from a donkey. The deviations 

 are far smaller. But every one knows how 

 difficult it is to distingTiish the common 

 oak from Quercus sessiliflora, or the lime 

 tree from Tilia grandifolia. Yet these are 

 forms which by the disciples of Linnfeus 

 are recognized as true species. And what 



