540 
E. G. Anderson 
PI pi — Purple anthers. A factor pair for pigmentation of anthers 
sheaths, pericarp, and so forth. (Emerson, 1921.) 
These three factor pairs interact to give the following plant color types 
described by Emerson (1921): 
A B PI — Purple 
A B pi — Sun red 
A b PI — Dilute purple 
A b pi — Dilute sun red 
a B PI — Brown 
a B pi — Green 
a b PI — Green 
a b pi — Green 
R r R° r r r° r ch — Red aleurone. A series of allelomorphs affecting antho- 
cyanin pigmentation in aleurone, sheaths, leaves, pericarp, anthers, 
and silks. (East and Hayes, 1911: Emerson, 1918, 1921.) 
P p — Pericarp color. Two of a series of allelomorphs for pericarp 
coloration. (Emerson, 1911.) The bronze type was so pale ii 
color that it could not be satisfactorily distinguished from white 
(colorless). Only two symbols are used herein, P for red pericarp 
and p for white or bronze pericarp. 
Y y — Yellow endosperm. (East and Hayes. 1911; Emerson, 1921.) 
Sm sm — Salmon silk color. Described in this paper. 
DESCRIPTION OF SILK COLORS 
The colors of silk in maize may be described as follows: 
1. Green (Plate L>. Silks light green, paler below husks; varying 
from a pure pale green to yellowish green. 
2. Red 'Plate LI). Silks green, as above, with the addition of a red 
anthocyanin pigment where exposed to light. The amount of red pig- 
ment may vary from a slight trace in the hairs, to sufficient to obscure 
the green color, giving the silks a deep or dark red color. The darker red 
silks frequently have some red below the husks. Emerson (1921) has 
shown this color to be due to the R factor. Microscopic sections show 
anthocyanin pigment in peripheral parts of the silks. 2 
5 The microscopic sections are prepared as follows: Pigmented tissue is fixed for from twelve to 
twenty-four hours in a saturated solution of mercuric chloride in 95-per-cent alcohol, and washed with 
95-per-cent alcohol without iodine. The usual paraffin method of embedding and sectioning is followed 
and the preparations are mounted in balsam without staining. Sections from 15 to 25 micra in thickness 
have proved satisfactory. 
