ABOUT PENSACOLA, Florida, occur all three of our native North American species of Linaria (Pennell, 1935, maps 82-84). These are: L. texana Scheele, which is widespread west of the Mississippi River but eastward is confined to the southern states; L. canadensis (L.) Dumort, common eastward, especially on the Atlantic Coastal Plain, and of scattered occurrence west of the Mississippi River; and L. floridana Chapman, of peninsular Florida and the Gulf Coast, with one record from the interior of Georgia. In April, 1941, the writer made mass collections of Linaria about Pensacola and at points inland as far as Atlanta, Georgia. The procedure consisted simply of taking mnany individuals from each patch of Linaria; a number of whole plants were taken and these were supplemented with inflorescences from many additional plants. If a patch had less than fifty individuals, each individual was ordinarily sampled; in very large colonies about fifty individuals were taken at random. It was found that any patch may consist of one species, or of two species, or of all three species intermixed. Table 1 shows the number of individuals of each species collected in each patch. The stations are arranged in order of distance from the Gulf of Mexico.2 ECOLOGY.-Soil requirements of the three species appear to be identical. About Pensacola, any patch of recently disturbed sand may have any or all species. Anderson (1933) observes that Iris versicolor and I. virginica, which appear to have entered the 1 Received for publication January 23, 1942. 2 For collections 1-6, distances are measured from the open water of the Gulf of Mexico on the south shore of Santa Rosa Island, and are computed from the chart of Pensacola Bay & Approaches, U. S. Coast & Geodetic Survey. The mileages for collections 7 and 8 are based on distances measured by automobile from Pensacola northward on U. S. Highway 29. Distances for collections 9 and 10 are measured on a Rand McNally map. southern peninsula of Michigan at different times, very rarely grow together. There is apparently no such exclusion of one species by another in the colonies of Linaria. Two species sometimes occupy the same habitat, but one is more limited than the other. Such a pair is Phyllitis Scolopendrium and Polystichum Lonchitis as they occur in Bruce Peninsula, Ontario. Where the Phyllitis is found the Polystichum is commonly found also, but the converse is not true, for the Polystichum is frequently found not accompanied by the Phyllitis. It would seem that the occurrence of the Polystichum is limited by a certain set of factors, and that of the Phyyllitis by the same set of factors plus others. The ranges of these two ferns are consistent with this hypothesis, for Polystichum Lonchitis, while somewhat local, is widespread in North America (Fernald, 1935, p. 207), but the American phase of Phyllitis Scolopendrium is known from but four small areas (Fernald, 1935, p. 200). This case is cited only to serve as a contrast with the Linaria situation. L. floridana is found, in this part of its retricted range, only along the Gulf of Mexico, and is quite absent from all collections not taken close to the coast. Yet where it does occur it outnumbers the two more widespread and presumably more aggressive species. Why does it fail to spread inland (except for the single inland collection recorded by Pennell, l.c.) ? There must be some factor, favorable to L. floridana and operative only along the coast (possibly climatic?), to which the other two species are indifferent. TAXONoMY.-These are three distinct species. All the specimens examined for table 1 had flowers or mature fruits, and most of them had both. There was no question of the specific identity of any individual. And yet L. canadensis shows many identical characters, on the one hand with L. texana, and on the Md.a 11:hPr wth r ;r'nn*in it. anVa IniTT rYrot