Gates, Tetraploid Mutants and Chromosome Mechanisms. i; 



is fertile, its (tetraploid) sporophyte producing diploid spores which 

 permanently fix the race. 



One of the most interesting facts discovered was a single case 

 (Phascum cuspidatum) in which the doubling in the number of 

 chromosomes, or rather the aposporous production of a diploid 

 gametophyte directly from the sporophyte, was accompanied by 

 mutational changes in the external characters. This mutant produced 

 no sex organs and was consequently sterile, but reproduced by 

 means of groups of cells resembling propagula, such as are found 

 normally in certain other mosses. This result shows, as I have 

 held, that mutational changes may occur at other points in the life 

 cycle than the reduction divisions. 



Another interesting paper dealing with polyploid chromosome 

 numbers, is that of Tischler (1910), who found in the banana 

 (Musa sapicntum] three races having reduced chromosome numbers 

 as follows: "Dole'' 8, "Radjah Siam" 16, and "Kladi" 24. He further 

 found that the volumes of the nuclei were in the ratio 1:2:3, 

 confirming the law I obtained with 0. yigas and 0. Lamarckiaiid. 

 Since the bananas are sterile, it is not evident how the tetraploid 

 and hexaploid conditions could have been arrived at through the 

 union of unreduced germ cells. 



Tahara (1910) has found 16 chromosomes as sporophyte number 

 in Crepis japojiica, which is the tetraploid number as compared 

 with 8 chromosomes reported by Juel (1905) in C. tectonun. Ishi- 

 kawa (1911) has also shown recently that while nine varieties of 

 Dahlia examined by him possessed 64 chromosomes, one species, 

 I), coronata, had only 32. Judging from his figures, the cells of 

 the tetraploid races are somewhat larger, though the individual 

 chromosomes are distinctly smaller. This condition does not fit the 

 anticipation either for a longitudinal or a transverse split of the 

 chromosomes. 



Very recently. Miss Pace (1912) has added another to the list 

 of tetraploid species by determining 15 as the X number of chro- 

 mosomes for Saxifraga sponhcmic-a, Juel (1907) having already found 

 30 as the A' number in S. granulata. And Bally (1912) has found 

 the X number of chromosomes in Aegilops orahi to be 16, which 

 is double the X number (8) in Triticum rulyarc and T. dicoccoides . 

 The determination of the number for wheat is a confirmation of 

 Nakao (1911), who found the X numbers to be 8 for wheat and 

 rye, and 7 for barley. AetjUops ovata is so closely related to Triti- 

 i-nni vulgare that the two cross freely and have been included by 

 some writers in the same genus. Bally found the heterotypic 

 chromosomes in T. dicocroides to be short and plump, while in 

 Aegilops they were elongated and with a hook for attachment to 

 the spindle fibres. He states that the latter were also about half 

 XXXIII. 



