1929] Navashin: Triploidy in Crepis 381 



TABLE 2 



The Chromosomal Constitution of the F, Plants Produced by Open 

 Pollination op Triploid C. capillaris Plant, ' ' 1947 ' ' 



Chromosomal 

 constitution 



in 



2r 



2n + I 



2n + I + I 

 3n 



Total 105 100.0 105.000 100.0 



The Fi plants were further investigated. From each of them a 

 sample of 100 open-pollinated seeds was taken and the root tips 

 secured after planting were studied cytologically. The chromosome 

 constitution of the Fo is tabulated in table 3. The figures of this 

 table, as may easily be seen, are essentially equivalent to those pre- 

 sented in table 2. As with F^, the Fo consists of a great majority 

 of diploids and triploids (888 diploids and triploids out of the total 

 959 plants) and only a negligible number (29 out of 959, i.e., about 

 3 per cent) of simple and double trisomies. It differs from Fj only 

 in the presence of a certain number of tetrasomics, tetraploids, and 

 a single 7n plant. 



In order to get data more nearly complete the triploid plants were 

 crossed by Miss Gerassimova inter se and also with diploid sister 

 plants. Man}' trisomic and polyploid plants Avere obtained from these 

 crosses and were carefully studied. The data concerning these experi- 

 ments will be reported in a later paper. 



TABLE 3 



Chromosomal Constitution of F. Plants ; cf. Table 2 

 Data of Miss Gerassimova. 



Chromosomal 

 constitution 



lin 



2n + I 



2n + I -f I 



3n 



3n + I 



3n + I + I 



4n 



7n 



Total 959 100.0 959.000 100.0 



Of the six theoretically possible trisomic types in C. capillaris five 

 were actually obtained and grown under controlled conditions. These 



