236 THE AMERICAN NATURALIST. (VoL. XXXVI. 
explanation of these facts is that beetles are only or mainly 
attracted to flowers by bright colors. If this explanation is 
correct, dull yellow must be an advantageous color for plants 
with freely exposed honey, protecting them from injurious guests." 
Subsequent observations of Müller himself showed that Bupleu- 
rum falcatum was very frequently visited by the beetle Mordella 
pumila. In Schlesien, Loew observed on Anethum graveolens 
5 species of beetles; numerous beetles were observed in the 
Tyrol by Schultz on Rhus cotinus, and on Euonymus both 
Schultz and Knuth observed beetles. The writer has found 
beetles very frequent visitors to the dull-yellow flowers of Acer 
spicatum. These illustrations need not be carried further, as 
it is evident that more extended observations have disproved 
Müller's generalization that dull yellow excludes the visits of 
beetles. i 
In the Umbellales both yellow and white have probably been 
derived directly from the primitive green. The involucre of 
Cornus canadensis changes from green to white, and the petals 
of many species of Cornus are green in the bud but become 
white as the flowers expand, while in the Umbelliferæ greenish- 
yellow flowers occur. In Apium one of the species is greenish 
yellow and two others are white. In Sanicula, S. gregaria has 
yellow petals exceeding the calyx and bright-yellow anthers, and 
S. marylandica has very small greenish-white petals and anthers. 
In Peucedanum three species are yellow and one white. White 
flowers may in some instances have been derived from yellow, 
as it has been shown that the yellow petals change to white in 
individual flowers in the Cruciferee. As regards attractiveness 
to insects the yellow flowers of the Umbelliferae do not appear 
to possess any advantage over their white competitors. 
In Thespium two of the species have yellow flowers, and in 
the third they are purple, with a common yellow variety. Many 
of the white species tend to become pink or reddish. In Daucus 
carota the central flower of the umbel, and frequently of the 
umbellets, is purple, and I have often seen the entire umbel 
pinkish. The coloration of this single flower can, of course, be 
of no advantage to the plant in attracting insects, and Darwin 
— a relic of a former ancient condition. I am 
