DISTRIBUTIONAL PATTERNS OF VERTEBRATES 435 



Texas (Potzger and Tharp, 1947, 1954). The determination that 

 spruce and fir pollens total 11% of the pollen in the lowermost foot 

 level in the Gause bog in Milam County was interpreted by the 

 authors as "adding to the accumulating evidence of a widespread 

 cool-moist climate, and migration of boreal genera far to the south 

 of the actual borders of the continental ice caps." On the eastern 

 coastal plain, Frey (1951) reported spruce and hemlock (Tsuga) 

 pollens from a profile from Singletary Lake, North Carolina, and 

 found a pine-spruce maximum at a zone of approximately 10,000 

 years age, determined by radiocarbon dating. Below this zone an 

 amelioration of climate is indicated, and above it successive changes 

 to warm, moist and to warm, dry are indicated. Spruce and fir 

 pollens have been reported from northern Florida, in Pleistocene 

 peats hypothesized as of late Wisconsin age (Davis, 1946). 



Pleistocene macrofossils of northern types have been recorded 

 from a few southern localities. Larch (Larix) has been reported 

 from northern Georgia (Berry, 1907). Remains of larch, spruce, 

 and arbor vitae (Thuja) have been found along Little Bayou Sara in 

 southern Louisiana (Brown, 1938). Braun (1955) attempted to 

 rationalize these southern records of northern plants with her argu- 

 ment against general displacement southward of climatic zones in 

 the Pleistocene. The hypothesis that frost pockets existed near the 

 coast and that cold, foggy climates prevailed there was suggested as 

 the explanation of the past occurrence of northern species on the 

 southern Atlantic coastal plain. She further suggested that ecologi- 

 cal requirements of the northern indicator species may have been 

 at one extreme of the tolerance range as manifested today. On the 

 contrary, the past occurrence of species that now live in the region 

 of the Little Bayou Sara deposits with the northern invaders can 

 more plausibly be explained by the assumption that they then 

 existed there at the limits of their cold tolerance, rather than that 

 the northern species were there with them because of their own 

 warmth tolerance. It seems quite unreasonable to attribute the 

 appearance of the presently cold-adapted species near the present 

 Gulf shores to any circumstance other than climatic change, and it 

 seems only reasonable on Dr. Braun 's own argument to attribute 

 their coexistence with present warmth-adapted species to the ability 

 of the latter to exist under conditions bordering the limits of their 

 cold tolerance. 



