. Contributions from the Botanical Laboratory, vol. 7. Botany; Botany. 266 INTERNATIONAL CONGRESS OF PLANT SCIENCES studies He also demonstrated the fact that the complete series of the chromo- somes of the 2n complex was duplicated in simply quadrupled cells after chloral treatment This indicated that in these cells chromosomal duplication by irregularities of distribution, and not by chromosome fragmentation, is the cause of the increase in number. This is an observation of great significance in genetical studies, where interbreeding of 2n and 4n races is often accomplished M. Navashin ('25)
. Contributions from the Botanical Laboratory, vol. 7. Botany; Botany. 266 INTERNATIONAL CONGRESS OF PLANT SCIENCES studies He also demonstrated the fact that the complete series of the chromo- somes of the 2n complex was duplicated in simply quadrupled cells after chloral treatment This indicated that in these cells chromosomal duplication by irregularities of distribution, and not by chromosome fragmentation, is the cause of the increase in number. This is an observation of great significance in genetical studies, where interbreeding of 2n and 4n races is often accomplished M. Navashin ('25) has carried further most skillfully the comparative studies of chromosome forms within a genus {Crepis), and has also traced the inheri- tance of these chromosomes in interspeciflc crosses, mutations, etc. Indeed, his work probably includes the first application of really critical observations on chromosome form to the analysis of genetical results in relation to the mheri- tance of specific chromosomes other than those concerned with sex. In this last respect the papers of Blackburn ('24) and of Allen ('19) are the most searching. This list of researches in the field of chromosome form is only partial, and the results embodied in shorter papers by scattered workers have built up a very valuable body of data. My own investigations (•24-'26) began with a study of the changes in form involved in the n and 2n vegetative and the meiotic divisions of Gasteria, giving a much more detailed discussion of the various stages than Sakamura had given for Vicia I'aba. The value of this lay in the indications it gave of the difficulties on analysis of the several stages and in the correlation of the forms assumed by the individual chromosomes in different stages. Later a similar study was reported for Velthemia. After finding that there was no recognizable variation among the species of the genus Castena available, a comparison was offered between the related genera Gasteria, Haworthta, a
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