Native Poplars of southern Alberta and their hybrids

A hybrid swarm involving all the species of poplars native to southern Alberta was observed and sampled. The samples were analyzed using Anderson\u27s methods : the scatter diagram and the hybrid index; and some of the stands were analyzed using a three-way modification of the hybrid index. Since no cultural methods were employed, the results of the analyses are considered to be tentative. The combinations postulated for the hybrids found are the simplest combinations that are thought to be capable of producing the observed effects. There are indications that crossing between the species of this region has been proceeding for many generations in natural alluvial habitats whose instability favours the establishment of hybrids. Direct hybrids between most of the species were observed. No direct hybrids between P. tremuloides and the section Tacamahaca were found, but other possible combinations were. Several individuals showing admixtures of characteristics of three species were found. Populus X Andrewsii appears to be a product of crossing between P. deltoides var. occidentalis and P. tremuloides