The inter- and intraspecific relationships of Holcus lanutus L. and H. mollis L. sensu lato (Gramineae)

Holcus lanatus and H. mollis were initially considered to be diploids, but their hybrids proved male sterile. Subsequent cytological studies showed H. mollis to be made up of a polyploid series with 2 n = 28, 35, 42 and 49. The planned hybridizations which then became possible showed the races to be fertile in varying degrees with each other and with H. lanatus. Self-fertile plants were found among all groups. Spikelets with two hermaphrodite functional florets were present within the panicles of many plants in the mollis groups and also in H. lanatus. Rhizomes were normal in H. mollis but never developed in H. lanatus. The chromosome races of H. mollis represent 'Cryptic' species since they cannot be separated on morphological criteria. A diploid H. mollis has been reported from Portugal.