[MATTHEW] FLORA OF THE LITTLE RIVER GROUP NO. II 81 



which in the figure has a scolloped outline. Unequal pressure of the en- 

 closing sandstone when the wood of the tree was in a soft, water-soaked 

 condition, has helped to produce the somewhat angulated form of this 

 tree trunk. 



The laxge size of the pith-cylinder in this species will be noted ; as 

 the trunk of the tree was split in two before fossilization only one-half is 

 preserved in this example, and this exhibits a pith-cylinder 2 inches by 

 % of an inch, giving a diameter of II/2 inches; but as this fossil has been 

 much compressed, it is probable that the original diameter was 2 inches. 



The seasonal layers of growth are, for the most part of the thickness 

 of the tree, quite regular and uniform, though here and there very close- 

 set layers are found in the inner part of the trunk, showing that the 

 season's growth was not always uniform. This perhaps indicates con- 

 siderable annual or seasonal variations in the climate of this region when 

 the tree was growing; or it may have been due merely to accidental 

 conditions surrounding the tree at the time of its growth. 



About one inch in thickness (&) of the trunk outside of the pith- 

 cylinder is defined by a narrow black line, and the outer half of this one 

 inch zone is more calcified than the rest. This zone has about 26 growth- 

 rings. Following this is a zone (c) of from IV2 to 2 inches across, where 

 the greatest disorganization of the tissues of the wood is found. It is esti- 

 mated from detached patches of the wood inJ this zone, where the layers 

 show more distmctly, that it contains about 35 seasonal layers. (The 

 greater disorganization of structure in this part of the trunk may be 

 due to rapid growth, which has resulted in a more porous or open tex- 

 ture, and one more liable to mineral replacement after the tree was 

 entombed. ) 



This zone is bounded on the outside by a second black band broader, 

 but less distinct than the one at its inner margin, and this outer black 

 band is followed by a white band (d) about half an inch wide, where there 

 is much replacement by white calcite, but in some parts the growth layers 

 are fairly well preserved ; this zone shows about 10 growth layers. 



A space of nearly an inch (e) forms another zone in which the sea- 

 sonal layers remain more distinct ; there are about 20 of these including 

 those of the black band that limits it without. 



Up to this point the thickness of the growth rings is comparatively 

 uniform, but beyond this there is a narrow zone (/) in which the layers 

 are much closer; in a quarter of an inch here there are 10 seasonal layers. 

 The thinness of the layers of this zone may mark a senile condition of 

 the tree when from some cause it was losing its vitality. 



No portion of the outer bark of this tree has been preserved, so there 



Sec. IV., 1909 6 



