Abstract
S. robustum as it is now known is basically a species of two cytological types, those with 2n=60 chromosomes, and those with 2n=80 chromosomes. Aneuploids, probable hybrids, and suspected hybrid derivatives also occur and exhibit a variety of chromosome numbers (2n=63-194) which have in the past suggested great cytological complexity in the species. The 60-chromosome types are known from Borneo, the Celebes, and Australian New Guinea. The 80-chromosome forms are found in Dutch and Australian New Guinea, on New Britain, and in the New Hebrides.
The following observations are also recorded for related species found in the geographic range of S. robustum: From the Celebes 2n=96 in S. spontaneuna; and from New Guinea 2n=80 in S. spontaneum, 2n=60 in Erianthus arundinaceus, and 2n=38 in Miscanthus floridulus.
