A Partial Map of Linkage Group D in Neurospora Crassa.

chromosomes are rather small, so it is quite likely that minor chromosome deficiencies or deletions would not be detected. Recently, we have obtained from commercial sources two spontaneous chromosome aberrants, one of which appears to be wholly tetraploid, while the other is chimaeric, containing diploid as well as tetraploid tissues. The first named is known to be, and the other probably is, a bud sport from William Sim. Both are redflowered. Both seem to be identical in appearasce with colchicine-induced tetraploids produced by Stewart8 and kindly shared 'with us. These aberrants will be subjected to genetic analysis as soon as suitable t4t0aploid test plants are available. Diploid test plants cannot be used so readily for4bis purpose because of very low seed production in crosses between tetraploids and diploids. Summary.-These results indicate that the carnation William Sim and four mutant clones, Pink Sim, White Sim, Peppermint Sim, and Skyline Frosted Sim, all have the same genotype: AA Ii Yy SS rr mn. The mutant clones thus are somatic variants, probably in the nature of periclinal chimaeras, with the mutant condition on the outside, but not deep enough to affect the formation of gametes. 1 M. B. Crane and W. J. C. Lawrence, The Genetics of Garden Plants (Nevy York: Macmillan Co., 1947); D. F. Jones, Bot. Rev., 7 (No. 6), 291 (1941); A. D. Shamel and C. S. Pomeroy, J. Heredity, 27, 487 (1936). 2 M. G. Kains and L. M. McQuesten, Propagation of Plants (New York: Orange JuddCo., 1949), p. 138. 3 R. E. Clausen and T. H. Goodspeed, Genetics, 8, 97-105 (1923). 4 G. A. L. Mehlquist, Proc. Amer. Soc. Hort. Sci., 46, 398 (1945). 5 T. A. Geissman and G. A. L. Mehlquist, Genetics, 32, 410 (1947). 6 G. A. L. Mehlquist and T. A. Geissman, Ann. Missouri Bot. Gard., 34, 39 (1947). 7 G. J. Dowrick, Gard. Ill., 69 (No. 12), 308 (1952). 8 R. N. Stewart, Proc. Amer. Soc. Hort. Sci., 57, 408 (1951).