450 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 



Table 2. — Chromosomal types in Datura Stramonium 



(Tho number of forms actually identified and the number theoretically possible are shown for each type. 

 Calculations are based on the assumption that the two parts into which a chromosome breaks are always 

 equal. Since this is known not to be the case, the figures given form a minimum. The Roman Figure I 

 indicates an unmodified or primary chromosome; II a secondary chromosome (with two like ends); III 

 a tertiary chromosome (with ends from two different primaries)] 



Cla.ss 

 No. 



Chromosomal types 



Formulae 



1-4 



5 

 6 



7 



In, 2n, 3n, 4n 



2n+I 



2n+n 



2n-!-III - 



2n+2 I 



2n+2 (I and II). 



2n+I+I 



2n+I+II 



2n+I+III 



2n+I+I+I 



2n-I 



2n+II-I 



2n-I+II-|-III 



2n-I+III+III 



2n-I+III+III+I 



2n-t-l free fragment 



2n+2 free fragments 



2n-i-l translocated fragment.. 

 2n-i-2 translocated fragments. 



3n+I 



3n-I 



4n-l-I 



4n-f2 I..-. 



4n+3 I 



4n-I 



4n+I-|-I 



4n+I-I 



,.4n-I.-I,-. 



4n+H-I-I-I. 



2n. 



2n (n-1). 



n. 



2n (I and II related) 



n (n-1) . 



2 

 2n (n-1) (I and II 



unrelated). 

 2n> (n-1). 

 n (n-1) (n-2) 



2n (I and 



lated). 

 2n (n-1). 

 2n (n-1). 

 2n' (n-1). 

 2n. 

 2n. 

 2n. 

 2n. 



n (n-1) . 



2 

 n (n-1), 

 n (n-1) . 



2 

 n( -l)(n 



II re- 



3) 



1 264 morphological types, but 528 different chromosomal types, if the parts of chromosomes which have 

 interchanged are considered. 



' 24 morphological types, but 576 different chromosomal types if ends to which fragments are translo- 

 cated are considered. 



