LINDSTROM, GENETICAL RESEARCH WITH MAIZE 347 
A second group of linked factors comprises the Ry pair of aleurone 
factors, the Li pair governing the yellow pigments (xanthophyll and 
carotin), and the Gg pair of chlorophyll factors (greengolden) as repor- 
ted by LINDSTROM (1917, 1918 and 1921). In this group Rr and Gg sho- 
* wed 23 per cent crossing over, altho later data indicate a somewhat 
smaller per cent. Factors Ll and Gg give approximately 19 per cent 
crossing over with limited data, and L/ and Rr are proven to be com- 
pletely linked (LINDSTROM 1921). The relative order of factors on this 
chromosome is as follows: — 
ie 20 G 

IE 
Unpublished data place Ws, another factor (complementary) for white 
seedlings, in this second group, since factors À an W, show about 17 
per cent cross-over. KEMPTON (1919a) places Ss (spotted aleurone) in 
this group since Rand S appear to be linked. HUTCHISON (1922b) states 
that Li (lineate leaves) also belongs here. 
A third group of factors showing linkage but independent inheritan- 
ce with respect to the other groups, involves the factor pairs Sw su 
(starchy-sugary endosperm) and Tu tu (normal-pod corn). The first re- 
port of this linkage was that of JONES and GALLASTEGUI (1919). More 
comprehensive tests of the situtation were made byW. H. Eyster (1921). 
He found about 30 per cent crossing over between these two factor 
pairs. In a later paper (1922a) he reports, using a total of 4624 back- 
crossed plants, an average percentage of crossing over of 28.63 + 0.45. 
Su 28.6 Tu 
VAN ee ee RE 

A fourth group consists of the Bb plant-color factors, the Lg lg pair 
for normal-liguleless leaves, and the Te te pair for normal-tassel ear 
plants (EMERSON 1920). The data reported by EMERSON give a three 
point test proving the fact of double crossing over in maize. The map 
showing the relative positions of these factors is as follows: — 
Lg 29.2 D 20.8 Te 
45.8 Le 
IN: 

A fifth group consists of the linked factors Y (yellow endosperm), 
Pl (purple plant color), sm (salmon silks), and wl (white seedlings). 
