Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915 Excerpt: ...of such pollen grains in gigas. The above-mentioned cross (see Table XII, p. 180) was also found to contain gigas-ke plants having 29 and 30 chromosomes. It seems very probable that these individuals came from the union of diploid eggs of lata having 15 chromosomes with gigas pollen grains having respectively 14 and 15 chromosomes. The bulk of the offspring from this cross, having 21, 22 and 23 chromosomes, obviously arise (a) from 7 lata + 14 gigas chromosomes, (b) from 8 + 14, occasionally 7 + 15, and (c) from 8 + 15. Miss Lutz has also obtained a mutant having 22 chromosomes, in the offspring of lata self-pollinated. This probably arose through the union of a 15-chromosome egg with a 7-chromosome male cell, although in all these cases the possibility of two haploid male cells taking part in fertilisation is not excluded. Hence there seems fairly strong evidence, although it is at present indirect, that diploid eggs occur both in lata and Lamarckiana, and that they can be fertilised. The plant having 20 chromosomes, in the F, of lata x gigas, very probably came from the union of an egg having seven chromosomes with a male cell having 13; and the plant with 22 chromosomes, derived from gigas x lata rubricalyx (see p. 191), doubtless came from 14? + 8 chromosomes. It remains to describe the chromosome distributions during meiosis in these triploid plants. We have devoted considerable study to this subject, but only the more general features, which are themselves of very great theoretical importance, can be considered here. In the first place it may be said that there is probably no essential difference as regards the behaviour of the chromosomes in triploid mutants or hybrids. Indeed, if triploid mutants originate, as we think most probable, through the uni...
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