GIGANTISM 



22- 



plants may be due to failure of such species to segregate or mutate 

 to dwarf ness. 



On the other hand, in certain exceptional cases increase of size 

 does not accompany the multiplication of the chromosome number. 

 The only autohexaploid flowering plant known (Rumex acetosa, 

 Yamamoto, 1935) is very much smaller than its triploid parent, 

 and in Anthoceros doubling does not produce the same increase as 

 in Funaria (Schwarzenbach, 1926). Similarly the autotetraploid 

 Lathyrus odoratus (Faberge, 1935) is no larger in stature than the 

 diploid [cf. Dorsey, 1936). It seems as though doubling will 

 increase the size of the normal type in most cases, but that some 

 organisms are more strictly adapted to a specific size, so that 

 particular genetic conditions influencing size, such as chromosome 

 number, may have a deleterious effect. This condition is perhaps 

 in part responsible for the general absence of tetraploidy amongst 

 animals. 



Table 35 



Measurements of Cells in Haploids, Diploids, and Polyploids 



I. (i) and (ii), Funaria hygrometrica, leaf gametophyte (v. 

 Wettstein, 1924). (iii) Crepis capillaris, dermatogen 

 (Navashin, 1931 b). 



II. Raphanus-Brassica hybrids (stomata) (Karpechenko, 1928). 



