514 BROOKLYN BOTANIC GARDEN MEMOIRS 
of seed. Because of this, the F; generation plants, in some cases, were 
grown in isolated cultures, instead of being bagged. In this way 
large quantities of seed were obtained for growing F. populations. 
In most cases, enough seed from bagged F; plants was obtained to 
check up the F» results from the unbagged seed. A large number of 
F; families were grown from seed of unbagged Fy, plants. The per- 
centage of cross-fertilization among the Fy» individuals appeared to 
be small. 
EXPERIMENTAL WORK 
Stem Color 
Stem color in castor beans can be roughly classified into five cate- 
gories (see Plates X XIII and XXIV)—bright green, green with reddish 
blush on sunny side, carmine or rose red, mahogany red, and purple 
(dark red). The development of each type of red coloration depends, 
to some extent, on sunlight, particularly the red blush class. In 
shade, plants of this class have green stems. 
These red color types are similar chemically, so far as solubility 
tests with their pigments are concerned, since all the red pigments are 
soluble in water containing a trace of chloroform, but remain insoluble 
in alcohol, xylol, or in pure chloroform. The red pigment is a sap 
color, occurring in the epidermal palisade cells in the leaf and stem 
(see Plate X XIII), also in parenchymatous areas of the stem, especially 
in the pith in some varieties. The different shades are apparently 
due (as observed microscopically) to different concentrations of the 
pigment in the cells and to a difference in the amount of pigmented 
cell area. From evidence thus far obtained, the writer is inclined to 
regard the hereditary differences between the red types as due to the 
presence and absence of several color dilution factors, each of which 
modifies the expression of a red pigment producing factor common to 
all, except, of course, the green-stemmed class. Still further modi- 
fications in coloration appear to be due to the presence and absence 
of a pattern restriction factor, in the absence of which the stems and 
leaves are mahogany red, or purplish red if ‘‘bloom” is present. 
In crosses, red blush X other red blush varieties always gave 
only red blush F, and F, offspring. Red blush varieties X green- 
stemmed varieties and the reciprocal always gave all red blush in Fy 
and approximately 3 red blush: 1 green in Fy». 
ACE allysOb tained esse eee tie eine 113 red blush: 43 green 
Mheoreticallyvexpected... 0-4 0540-5 1G FG flail des 200 
In F3, seed from unbagged Fy. green-stemmed plants generally gave 
all green plants, while unguarded seed from Fy, red blush plants either 
gave all red blush or both red blush and green-stem families. 
