Variant Chromosome Numbers in Sphaerocarpos

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Abstract
Four classes of gametophytes of S. donnellii were examined cytologically. A dwarf and a cupulate mutant, which developed from spores of pedigreed sporo-phytes, have in each case a haploid chromosome complement of 7 autosomes and 1 Y chromosome.[long dash]In harmony with previous results, gametophytes developed from spores of dyads are diploid, or approximately diploid, with (in the cases studied) 1 X and (usually at least) 1 Y chromosome. [long dash]The viable progeny of a triploid sporophyte possess, so far as has been found, no irregular chromosome complements; in each of the clones of such origin studied the diploid autosome number (14) was present.[long dash]In the cases studied, gametophytic offspring of tetraploid sporophytes are diploid; the [male][male] have 2 Y chromosomes; the apparent [female][female] have 2A + X + Y; the latter are probably (in one case certainly) intersexual.[long dash]Additional viable sporophytic chromosome complements here reported are 4A + X + 2Y and 4A + X + 3Y, those previously observed being respectively 2A + X + Y, 3A + X + Y, 3A + X + 2Y, and 3A + 2X + Y.

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