HETEROPLOIDY 



343 



10, 30, 40, 80, and certain aneuploid numbers. Euploid individuals and 

 races are now known in a large number of species in many groups of 

 plants. In (Enothera Lamarckiana, where the diploid (2n) number is 14, 

 some of the well-known mutants have 471, 3w, and 2n + 1 chromosomes. 

 The primary and secondary mutants of Datura stramonium are 2n + 1 

 forms. In Thalidrum minus there are three races (species ?) with gametic 

 numbers of 7, 14, and 21. Vicia grceca has races with 6, 7, and 14. In 

 Matthiola incana have been seen individuals with 14, 14 + two fragments, 

 and 7 + one fragment. In Pellia epiphylla and P. Neesiana races with 

 diploid gametophytes are known. In 

 Funaria hygrometrica there are races with 

 14, 28, and 56. A few such cases are 

 known among the algae. Among grains cer- 

 tain speltoid wheats, dwarf wheats, and 

 fatuoid oats may have one or two chromo- 

 somes more or less than the normal number. 

 In Artemia salina, a crustacean, there are 

 diploid, tetraploid, and octoploid races. ^^ 



Heteroploidy within the Individual. — 

 Occasionally one region of an individual 

 differs from the remainder in chromosome 

 number. Diploid Datura plants, for example, 

 have been seen to bear 2n + 1, 2n — 1, and 

 4w branches. Sometimes the modified region 

 is a well-defined sector of the plant (Figs. 



195,204).!^ The differing portions may also somal chimera in Nicotiana. 

 , , J • 11 • n • • ii Cells at left of heavy line have 24 



be arranged concentrically: m Spinaaa the chromosomes, as at a; cells at 

 plerome and dermatogen may be 2w and the right have 48, as at b. {After 

 periblem An or 8m. ^^ Such sectorial and " ^' 



periclinal types are known as "chromosomal chimeras. " Of very 

 frequent occurrence are scattered cells with aberrant numbers, especially 

 in roots or anthers subjected to abnormal cultural conditions. The 

 formation of tetraploid shoots is sometimes induced from callus tissue 



Fig. 195. — Portion of trans- 

 verse section of root of chromo- 



" Randolph and McClintock (1926) and Randolph (1932) on Zea; Blakeslee, 

 Belling, and Farnham (1920) on Datura; Kuhn (1928o) on Thalidrum; Sweschnikova 

 (1927a) on Vicia; Lesley and Frost (1928) on Matthiola; Heitz (19276) and Showalter 

 (1927c) on Pellia; von Wettstein (19246) on Funaria; Winge (1924), Huskins (1928a6, 

 1931a), Mtintzing (1930a) and Hakansson (1933a) on Triticurn; Huskins (1927, 1928a) 

 and Nishiyama (1931) on Avena; Artom (1912) and F. Gross (1932) on Artemia. For 

 (Enothera, see footnote 5, p. 334. 



18 Nawaschin (1926, 1930a) and HolUngshead (1930c) on Crepis; Lesley (1925) on 

 Lycopersicum; Ruttle (1928) on Nicotiana; Jaretzky (1927a6) on Thalictrum. Langlet 

 (19275) lists known cases. 



•' De Litardiere (1923c) and Langlet (19276) on Spinacia and Cannabis. 



