CELL-SIZE 221 



influence the size of the cell and of its nucleus, but, these factors 

 being equal, the size might be expected to be proportionate to the 

 number of chromosomes of which the nucleus is constituted when 

 the number is simply doubled or halved. This condition is realised 

 immediately after the formation of a new nucleus in the pollen. 

 Diploid pollen grains have 1-25 times the linear dimensions and 

 twice the bulk of haploid pollen grains (Belling on Uvularia, 1925 ; 

 Solanum, Fig. 67). The same applies with certain restrictions 

 to the cells of all parts of the organism, and is equally true of the 

 polyploid derivatives of hybrids and pure forms, as shown by 

 V. Wettstein (1924) with diploid, tetraploid and octoploid mosses, 

 and by the other authors cited. 



Table 34 

 Observations of Cell Size in Haploids, Diploids and Polyploids 



Animals : — 



Drbsophila melanogaster {x, 2x, jx) 



Artemia salina {2x, 4X, wild races) 



Trichoniscus provisorius {2x, jx, wild 

 races) .... 



Plants : — 



Datura x, 2x, 4x) 



Crepis {x, 2x) .... 

 Crepis capillaris {x, 2X, jx, 4X) . 

 (Enothera {x, 2x) 



Raphanus-Brassica {2x, jx, 4X, 6x) 



Nicotiana digluta {2X, 4x) . 



Funaria, etc. {2x, 4X, 8x) 



Uvularia {x, 2x) 



Solanum {x, 2x) 



Tradescantia {x, x -{- 1, x -\- 2, etc.) 



Bridges, 1925 b. 

 Artom, 1928. 



Vandel, 1927 h. 



Blakeslee, 1922 ; Belling and 



Blakeslee, 1927. 

 Hollingshead, 1928. 

 Navashin, 1931 h. 

 Emerson, 1929 ; Gates and 



Goodwin, 1931. 

 Karpechenko, 1927, a and b. 

 Clausen and Goodspeed, 1925. 

 V. Wettstein, 1924. 

 Belling, 1925 (pollen grains). 

 Jorgensen, 1928 (pollen grains). 

 D., 1929 c (pollen grains). 



While the proportion between size and chromosome number is 

 fairly closely maintained so far as cells are concerned, intracellular 

 structures such as chloroplasts may be increased in number instead 

 of in size, and multicellular structures are developed in changed 

 proportions. The vigour of the organism as a whole is usually 

 reduced by either reduction or multiplication of the chromosome 

 number, and its size therefore does not change proportionally. 

 The genotype of the new haploid or polyploid is still adapted to the 

 cell size of the ancestral diploid and works less favourably under 

 new conditions. A reduction in the number of cells in corresponding 



