330 ANNUAL REPORT SMITHSONIAN INSTITUTION, 195 4 



are planted, every grain on the ear borne by the plant from the red 

 grain is red. For about 10 years the writer has had a strain of 

 Calico maize in culture for another purpose. During that time, four 

 ears have been found, each with a block of grains with colorless peri- 

 carp (pi. 5, fig. 23). Wlien these colorless-pericarp grains are 

 planted, ears are borne, every grain of which is colorless. This may 

 represent a mutation in the unstable gene to one that is stable as far 

 as colorless pericarp is concerned. 



Mutations may occur in the formation of gametes, or in any living 

 vegetative or somatic cell. In vertebrate animals and in some plants, 

 mutant cells in somatic or vegetative tissues are lost with the death of 

 the individual or at least death of the organ in which it occurred. 

 This has given rise to the too common notion that mutations only 

 occur in the formation of gametes. No techniques are known at pres- 

 ent by which pieces of somatic tissues or organs of vertebrate animals 

 or the vegetative organs of some plants can be used in the propagation 

 of such organisms. However, most seed plants may be propagated 

 vegetatively from leaves, stems, or roots. A mutant cell in any one 

 of these organs then has a chance of survival, providing the 

 organ is placed in proper conditions which will lead to vegetative 

 multiplication. 



If a mutation occurs in a gamete or in the fertilized egg, every cell 

 of the embryo is identical to the zygote, as far as chromosomes and 

 genes are concerned. This continues to be true for all cells of the 

 seedling as well as the mature plant. This was mentioned earlier 

 when dealing with growth and development of maize zygotes. Or- 

 dinarily when this happens, the mutant individual may be found among 

 many individuals of the parent type which do not exhibit the change. 

 An example of such a mutant is illustrated by Ulrey's variegated 

 African violet {SaintpauUa) (pi. 7, fig. 26). This variegation 

 is due to a chlorophyll deficiency in the young leaves, and is gradually 

 lost as the leaves become older, with old leaves often being entirely 

 green. More variegated plants may grow vegetatively from leaf 

 cuttings. 



Previously it was mentioned that mutations may also occur in any 

 vegetative or somatic cell. This may be illustrated by the African 

 violet variety sold as "Orchid Wonder." The leaves of this variety 

 are ordinarily dark green in color. The plant illustrated by figure 

 27 (pi. 7) grew vegetatively from the petiole of a detached leaf of the 

 Orchid Wonder variety when placed in moist sand. The chlorophyll - 

 deficient tissue resulted from a cell that mutated in the stem primor- 

 dium which developed near the cut end of the petiole of the detached 

 leaf. As the stem primordium gi-ew, the mutant cell increased in 

 numbers and the chlorophyll-deficient tissue became distributed in 



