have been the most intensively studied. Because of com- 
mercial mining for centuries, large volumes of material 
have been available for examination. From 1845 to the 
present, more than 70 papers have presented systematic 
descriptions of plant inclusions, most of them written 
during the late 19th Century. Attempts to assess the 
total flora were not initiated until 1937, but 750 taxa 
had been reduced to 215 by 1960, and the geographical 
affinities of the flora were being discussed. The kinds 
of trees which produced the resin, the causes and nature 
of excessive resin production and the composition of the 
forest were considered in 1890, but there was little sub- 
stantiating evidence. Recent work, using the lackfilm- 
method to study anatomically the bark and wood, rein- 
forced the widely held view that the resin was produced 
by pines in the Baltic area. However, the variety of 
physical and chemical properties suggests a multiple 
source for at least some of the material. ‘‘Swamp trees’’ 
have been presented as possible resin producers on the 
basis of cupressoid foliage and aquatic inclusions. Possi- 
ble raodern equivalents of amber forests have been dis- 
cussed recently, but no actual investigation of these 
equivalents has been made. Notwithstanding a relatively 
large background of information about plants in the Bal- 
tic amber, much still needs to be done in synthesizing the 
data and correlating them with present-day conditions. 
A more thorough study of the resins associated with 
the German brown coals might produce illuminating 
results, because corroborative evidence from wood, fruits 
and seeds, leaf cuticles and pollen is available. Thus far, 
resins from taxodiaceous and cupressaceous sources, as 
well as from Liquidambar, have been identified. 
Although little information is usually available regard- 
ing the plant sources of ambers from other geographic 
areas, a variety of trees seems to be indicated. ‘The Cre- 
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