+-----------------+------------+-------------+--------------+ | Gens. | Total. | Cross- | Cross-over | | | | overs. | values. | +-----------------+------------+-------------+--------------+ | Yellow bifid | 3,175 | 182 | 5.8 | | White bifid | 20,800 | 1,127 | 5.3 | | Bifid vermilion | 2,509 | 806 | 32.1 | +-----------------+------------+-------------+--------------+ {30} In the crosses between white and bifid there were 1,127 cross-overs in a total of 20,800 available individuals, which gives a cross-over value of 5.3. In the crosses between yellow and bifid there were 182 cross-overs in a total of 3,175 available individuals, which gives a cross-over value of 5.8. In crosses between bifid and vermilion there were 806 cross-overs in a total of 2,509, which gives a cross-over value of 32.1. On the basis of all the data summarized in table 65, bifid is located at 6.3 to the right of yellow. LINKAGE OF CHERRY, BIFID, AND VERMILION. In a small experiment of our own, three factors were involved--cherry, bifid, and vermilion. A cherry vermilion female was crossed to a bifid male. Two daughters were back-crossed singly to white bifid males. The female offspring will then give data for the linkage of cherry white with bifid, while the sons will show the linkage of the three gens, cherry, bifid, and vermilion. The results are shown in table 3. TABLE 3.--_P_1 cherry vermilion [female] [female] x bifid [male] [male]. B. C.[2] F_1 wild-type [female] x white bifid [male] [male]._ |----------------------------------- | | F_2 females. | | |---------------------------+ | | | |Refer-| Non-cross- |Cross-overs. | |ence. | overs. | | | |-------------+-------------+ | |White-|Bifid.|White-|Wild- ~ | |cherry| |cherry|type. ~ | | | |bifid.| | |------+------+------+------+------+ | 262 | 40 | 46 | 1 | 2 | | 263 | 47 | 45 | 3 | 3 | | |------+------+------+------+ |Total.| 87 | 91 | 4 | 5 | |-----------------------------------