340 INTRODUCTION TO CYTOLOGY 



A chromosome complement in which the heteroploidy is due to the 

 multiplication of a single kind of monoploid set (or of some of its members) 

 is said to be autoheter opioid; whereas, one in which specifically different 

 sets or members are combined, as in a hybrid, is alloheter opioid. Although 

 this distinction cannot always be sharply drawn, it is of considerable 

 importance, as will appear later.- 



-'^^^' Ak Mi 



^k 





D 



Fig. 193. — Somatic chromosome complements of various species of Rosa, illustrating 

 euploidy. A, R. webbiana, 14 chromosomes. B, R. chinensis, 21. C, "Konrad Ferdinand 

 Meyer," 28. D, R. tomentosa cuspidatoides, 35. E, R. nutkana, 42. F, an octoploid 

 hybrid, 56. {After Tackholm, 1922.) 



Heteroploidy in Related Species. — Very often the chromosome 

 numbers in the various species of a given genus form a more or less 

 complete euploid series (Fig. 193). For example, in Chrysanthemum the 

 various species have 9, 18, 27, 36, and 45 pairs of chromosomes; hence 

 they range from diploid to decaploid, with 9 as the "basic" number 

 (Tahara, 19156, 1921). In Potentilla, with 7 as a basic number, the 

 species range from diploid to 16-ploid.^ The species of Thalidrum, also 

 with 7 as a basic number, range from diploid to 12-ploid.'* Such long 



2 In many reported cases it is not known which type of heteroploidy is represented. 

 It is largely for this reason that "heteroploidy" is here used singly and in combination 

 to indicate number only, without special reference to the kinds of sets concerned. In 

 this we follow Winkler (1916, 1920). Winkler refers to complements with similar sets 

 (genoms) as " isogenomatic " and to those with unlike sets as "anisogenomatic." 

 The terms "autopolyploidy " and "allopolyploidy" were suggested by Kihara and 

 Ono (1926). Hurst (19276) uses the parallel terms "duplicational polyploidy" and 

 "differential polyploidy." Tackholm (1922) introduced "euploid" and "aneuploid." 

 For further discussions of terms, seeLanglet (1927a), Brieger (19276), and von Wettstein 

 (1927). 



3Shimotomai (1929, 1930), Miintzing (1931). 



^Langlet (1927a), Kuhn (1928a, 1930c). 



