334 ANNUAL REPORT SMITHSONIAN INSTITUTION, 195 4 



forming a border to the leaf, is genetically different from the green 

 tissue. To test this inference, leaf cuttings were made as illustrated in 

 figure 36 (pi. 9). This was done because roots develop from the cut 

 end when in contact with moist sand. However, ordinarily roots de- 

 velop only from the green tissue of the leaf cutting and not from the 

 yellow tissue. New shoots or stems initiate at the base of a root about 

 where the root originates from the leaf tissue. A block of all-green 

 tissue was removed from the area of the leaf cutting that was to be set 

 in moist sand, with only strips of yellow tissue in contact with the 

 substrate. Roots, after some time, developed from the yellow tissue 

 and eventually golden-yellow shoots as illustrated in figures 36 and 

 37 (pi. 9). At first the shoots are slightly green, indicating the pres- 

 ence of some chloroplasts, but these soon disintegrate and the tissues 

 become golden yellow in color. If the rhizome connection between the 

 yellow shoot and the leaf cutting is broken, the shoot dies of starva- 

 tion within about 2 weeks. This is presented as evidence that the yel- 

 low tissue is genetically different from the green. The yellow tissue 

 is mutant tissue that has existed in a chimaeral relationship with 

 green Sansevieria tissue, perhaps much longer than the 50 years since 

 the French botanist Laurent discovered it in cultivation by natives of 

 the Belgian Congo. It is only by accident, or when special technique 

 as described above is applied, that segregation of the pure yellow 

 mutant tissue results in chlorophyll-deficient plants. 



Mutations resulting in sectorial chimaeras may occur in leaves, 

 stems, roots, inflorescences, flowers, and fruits. The grapefruit illus- 

 trated by figure 39 (pi. 10) had a relatively large sector of the fruit 

 coat or pericarp that was dark brown in color in contrast to the light- 

 yellow color of the remainder of this particular fruit. No differences 

 were observed in the carpels containing the pulp opposite the brown 

 sector of the pericarp and those opposite the yellow part of the fruit 

 coat. The inference from this and other evidence was that only the 

 sector of the pericarp was affected by this mutation and that the 

 carpels and seeds opposite the brown sector were not changed. Simi- 

 lar sectoring is fairly frequent in oranges, lemons, and grapefruit. 



Sectorial chimaeras in fruits are not always superficial, i. e., limited 

 to the pericarp. Several years ago there was found in a field a tomato 

 fruit of the Baltimore variety (pi. 11, fig. 40) that had a sharply 

 outlined yellow sector with the adjoining parts a deep red color. 

 Eventually a cross section of the fruit was made in order to examine 

 the extent of the yellow mutant tissue of the sector. It was readily 

 evident that the yellow tissue extended to the center of the fruit and 

 included two seed cavities. 



Seeds from the yellow sector were saved, as well as those from the 

 red portion of the fruit. Three plants from seeds of the yellow sector 



