Variant Chromosome Numbers in Sphaerocarpos

1. A dwarf and a cupulate male mutant, which developed from spores of pedigreed sporophytes, have in each case a haploid chromosome complement of seven autosomes and one Y chromosome. 2. In harmony with previous results, gametophytes developed from spores of dyads are diploid, or approximately diploid, with (in the cases studied) one X and (usually at least) one Y chromosome. 3. 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. 4. In the cases studied, gametophytic offspring of tetraploid sporophytes are diploid; the males have two Y chromosomes; the apparent females have 2A+X+Y; the latter are probably (in one case certainly) intersexual. 5. 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.