THE CLIMATE OF ACADIA IN THE EARLIEST TIMES. 17 



When cut across, these trees show distinct annular rings 

 of growth, proving that the plant had alternate periods of 

 rapid and slower increase. They had very large pith- 

 cylinders as compared with those of our living coniferous 

 trees ; these cylinders are sometimes as much as an inch 

 across ; and if the large pith had the same significance as it 

 has in modern plants, the trees had a rapid growth. 



The microscope reveals a beautiful structure in the 

 Devonian trees. Side by side lie immense numbers of little 

 cells, which went to build up the trunk of the tree, and 

 each of these cells carries a number of pores along its walls, 

 arranged m several crowded rows, running lengthwise in the 

 cell. Even with the naked eye one can see the medullary 

 rays that radiate from the pith cylinder to the outer surface of 

 these old Devonian trees. Thus in these trees entombed so 

 many ages ago you may see the whole economy of structure 

 of the trunk as we have it in modern trees, the central pith 

 so important, especially in the early growth of the plant, the 

 vascular or woody tissue, of which the principal part of the 

 trunk was composed, and the medullary rays that serve to 

 unite the centre of the tree with its periphery, and portions 

 of the bark that once enveloped the whole. 



Such are the morphological conditions of the tree ; but 

 you may also in these trunks study the effect of dynamical and 

 chemical action in rending apart the layers of the tree and 

 filling the space with a wedge of calcite, or else in replacing 

 the substance of the wood by a siliceous deposit. But this is 

 apart from our subject, which was to show by the mode of 

 growth in these trees that the earth at that early period of 

 Devonian time possessed seed-time and harvest, if not sum- 

 mer and winter. It is true that man did not witness this 

 sowing and ingathering, but he may still glean of the harvest 

 and pick up the spare seeds that escaped the germinating 

 influence of the Devonian soil. 



This smiling Devonian country, covered with vegetation 

 and teeming with life, existed but for a time. Rougher con- 

 ditions supervened, the sandy beds became coarser, and fewer 



