38o NATURAL SCIENCE. 



JULY. 



such cases where Pine woods spread unhindered over wide tracts of 

 country. We may note some of the results obtained by an applica- 

 tion of experience gained in recent forests, to the interpretation of 

 the fragmentary relics of Tertiary forests. 



In modern forests a variety of causes produce resinous exuda- 

 tions ; resin ducts and receptacles are tapped by branches falling 

 from the lower parts of stems where they are unable to secure their 

 proper share of light and nourishment, and eventually decay and 

 fall. A falling tree crashes through the branches of its neighbours ; 

 wind, storms, and lightning tear off branches or splinter stems. From 

 all such causes resin receptacles are opened up and exudation results. 

 The scars left by broken branches invite the attacks of animals and 

 parasitic plants, which, in their turn, injure the living tissues and 

 increase the flow of resin, which, softened by the sun's heat, may 

 spread over the surface of branches and stems, enclosing in its 

 course splinters and loose fragments of wood, and sealing them up, 

 to be eventually entombed in hard, clear Amber. Insects, flowers, 

 leaves, twigs, and light fragments, are carried by wind or other 

 agency to the soft resin and embedded in it. 



In addition to the Amber formed in this way, it has frequently 

 happened that resin has been hardened and preserved in the ducts 

 or cells from which it had never exuded. To compare the included 

 insects and plants with living species is fairly simple, and such a 

 comparison gives us a good idea as to the life in the Amber woods. 



Leaving out of consideration the fossil insects, and avoiding 

 detailed lists of plants, we may briefly refer to some of the better 

 known or more interesting genera. Abundant evidence is afforded 

 by plants of various families that the Amber flora flourished in a- 

 subtropical climate. 



Beginning with Dicotyledons, we note the presence of such 

 familiar genera as Fagus, Acer, Castanea, and Quercus, represented 

 by leaves, flowers, fruits, &c. 



In addition to these genera there are many others belonging 

 to the same class, of which we may note some of the more familiar 

 and interesting families. 



CuPULiFER^. — Specimens of Quercus are common in the Baltic 

 Amber ; for the determinations of the various species we are chiefly 

 indebted to Caspary and Conwentz. The pendant male inflorescence 

 of Quercus piliger a (Conw.) figured by Conwentz (3, vol. ii.) is a striking 

 example of a fossil whose surface characters are seen through the 

 clear Amber scarcely less distinctly than if a fresh flower were 

 before us. In the same Family we have four species of Castanea, also 

 leaves and floral organs of Fagus. 



DiLLENiACEiE. — This tropical and Australian Family has a repre- 

 sentative in Hibhertia, a genus native in extra-tropical Australia, 

 whose leathery leaves with grooved and hairy bwer surface are well 

 shown in Conwentz's figures. 



