160 BOTANICAL GAZETTE {AUGUST 
Meehan (6, 18) referring to the fact that R. copailina, venenata 
and /oxicodendron. are variously classed as dicecious, polygamo- 
_ dicecious, or polygamous, insists that they and R. cotinoides are 
all truly dicecious. I regard R. glabra and Canadensis as dice- 
cious. s 2 
In regard to the staminate, perfect, and pistillate flowers of 
R. Cotinus, Miller observes that they decrease in size in the 
order mentioned, and that, consequently, most insects visit them 
in the most advantageous order. Schulz failed to confirm the 
latter observation. In R. glabra and Canadensis, 1 think insects 
prefer the staminate flowers, partly because they are more 
conspicuous and because they contain pollen as well as nectar, 
and that the order of their visits is advantageous. However, 
I do not believe that natural selection has operated im pro 
ducing the difference, and so hold that it would be erroneous 
to say that the difference exists to secure the advantage. Age 
rule stamens are more conspicuous than pistils, and it is quite 
abvious that a small flower containing five stamens will be aa 
evident than one containing a single pistil. The larger pet 
anth may be explained as existing to support, and at first £0 
protect, this exterior set of organs. 
Two effects upon the insect visitors have been attributed 
the dull yellow colors of Rhus. Miiller says that &. Cotinas, like 
all other flowers of a dull yellow color, is almost completely 
avoided by Coleoptera. The general proposition is denied by 
Bonnier (9), and Schultz says that it is not true for R. ee 
in the Tyrol, where he found many beetles among the oT. - 
Pastinaca, on which I have taken forty species of beetle oy 
mentioned by Miiller as an example of the same kind. — ant - 
The idea that the flowers of Rhus were specially age f 
to flies (macromyiophilous) seems to have originated with - -~ — 
pino(5). The “Tipo ramnaceo,” which he regards as macromy” a e 
philous, includes the greenish yellow species of Rhits, ki ae 5 
Luonymus, Euphorbia, etc. In a special paper on the » a 
ical significance of flower-colors Miiller (12) says that Br 
citys the 
yellow colors are frequent in flowers among whose visi 
