HETEROPLOIDY 



349 



morphology is well known, inspection of the complement in the root tips 

 enables one to tell whether a single set has been multiplied to produce an 

 autoheteroploid type or unlike sets have been combined to make an 

 alloheteroploid one. Similarly, one may often tell whether an apparently 

 2n + 1 type has arisen through the duplication of a chromosome by 

 non-disjunction (Fig. 198, E), or through the fragmentation of a chromo- 

 some (Fig. 198, F), or through hybridization (Fig. 206, 3). Furthermore, 



c, AC, 



h 



Fig. 198. — Somatic chromosome complements in Crepis, showing autopolyploidy and 

 other conditions. A, triploid complement in C. capillaris. B, pentaploid complement 

 in C. capillaris. C, diploid complement in an individual "asymmetrical" for size of 

 satellites. D, tetraploid complement in C. tectorum. E, hyperdiploid complement in 

 tectorum plant with extra B-chromosome. F, diploid complement in tectorum plant with 

 one D-chromosome fragmented into two portions: Do and d. {After M. Nawaschin, 

 1926.) 



a sufficient knowledge of the chromosome morphology in an organism 

 under investigation makes it possible to detect alterations, such as 

 deletions and translocations, not affecting the number of chromosomes 

 present. The occurrence of such alterations makes it necessary to use 

 the criterion of chromosome morphology with considerable caution. 



Other criteria of value in the analysis of heteroploid complements 

 are the meiotic behavior of the chromosomes and their functions as 

 indicated by genetic data. Autoheteroploids and alloheteroploids 

 frequently differ characteristically in their meiotic and genetic behavior. 

 It is the purpose of the next two chapters to describe some of the most 

 important of such phenomena. 



