factors might determine abundant resin production. 
Studies were also made of the reactions of Pinus sylvestris 
L., P. strobus L., P. nigra Arn., P. ellottii Englm., P. 
palustris Mill, and P. oocarpa Scheid. to artificial wound- 
ing. Samples of wood and bark from wounded trees of 
different ages were studied physiologically by micro- 
chemical techniques. After a certain period of time, other 
samples were taken above and below the first wound for 
both anatomical and physiological investigations of the 
production of resin around the wound. These experimen- 
tal approaches offer the best solutions to many of the 
unanswered questions, but they will have to be continued 
for considerable time before the answers are obtained. 
Other investigators, such as Klebs (Kunz, 1903), have 
thought that ‘“‘normal’’ trees could produce adequate 
amounts of resin to account for the amber accumulation. 
He compared the amount of resin produced commer- 
cially from such trees as Pinus nigra Arn., P. maritima 
Poir., P. sylvestris L. and Abies excelsa DC. He then 
calculated that approximately 11 kilos per cubic meter 
of amber was obtained from the blue earth in 1902. A 
tree of P. nigra between 60 and 80 years old requiring 
a surface of about ten square meters, produces 120 kilos, 
or over ten kilos more than the same surface area of am- 
ber pine. Furthermore, P.nig7a does not produce as much 
resin as many other pines, especially certain species liv- 
ing in warm temperate regions. Klebs thus concluded 
that, when not just one pine but generations of them 
covering a vast area are considered, no special conditions 
appear to be needed to account for the concentration of 
amber. ‘This does, however, assume that there were 
mechanisms for naturally injuring the trees comparable 
to that done commercially. Bachofen-Echt (1980, 1949) 
also thought that this material could be accounted for 
as a result of amber forests persisting over an extensive 
area for millions of years. 
[ 258 ] 
