A Partially Fertile Triple Species Hybrid in Nicotiana.

Crosses between three distinct species in Nicotiana are comparatively rare, only nine having appeared in the literature on this genus. The one here reported upon, (rustica Xpaniculata) x Langsdor i , as well as (rustics X Tabacum) Xpaniculata, and (rustica X paniculata) XgZutinosa, was produced in Europe many years ago (EAST 1928) but has not been studied much since. In 1930 KOSTOFF also described such a triple hybrid combination, as well as Tabacum var. sunguinea X (Langsdor i XSanderae), and listed five others which he had secured, as follows: (rustica Xpaniculata) XSanderae, Tabacum X (sylvestris X Rusbyi), Tabacum X (Rusbyi Xtomentosa), (glauca XLangsdor-i) XSanderae, and (glauca X Langsdor$i) x d a t a . His plants of the (rustica Xpaniculata) x Langsdorfii combination, however, were sterile and evidently differed fundamentally in chromosome constitution from mine. I t may be noted that in three of the hybrids just listed, two of the alataLangsdor$Ei-Sanderae group, which cross freely together giving fully fertile hybrids with perfect pairing of chromosomes, are combined with a third species. These three, then, might reasonably be expected to be comparatively easy to secure. In two other cases two of the 12-chromosome Tabacum-like species, tomentosa, sylvestris and Rusbyi, are combined with Tabacum. In only one other case, (rustica XpanicuZata) XSanderae, besides the one here described, do three species having different chromosome numbers enter into the hybrid combination. This combination is very similar to mine, Sanderae having the same number (9) of chromosomes as Langsdori .