Dr. B. Seemann on the Mammoth-tree of Upper California. 169 



scientific public still fancy the age of 3000 years, originally 

 allotted to the tree in question by vague computation, may still 

 be considered as correct, — quite overlooking that Dr. Torrey, 

 counting the layers on a complete radius of another trunk, about 

 the genuineness of which there was no doubt, has furnished the 

 following data : — 



"The 1st hundred layers occupy a breadth of 17^ inches. 



2nd „ „ „ 14 „ 



3rd „ „ „ 121 ,, 



4th „ „ „ 13 „ 



5th „ „ „ 16i „ 



6th „ „ „ 8f „ 



7'th „ „ „ 7f „ 



8th „ „ „ 11 „ 



9th „ „ „ 10 „ 



10th „ „ „ 11 



11th „ „ „ Hi „ 



The remainder of 20 layers occupies over 1 inch: 1120 layers 



corresponds so closely with Dr. Lindley's estimate [of Sequoia Welling- 

 tonia\], that we may supjjose him to have employed equivalent data in 

 a similar manner. How great a deduction must we make from this esti- 

 mate, in consicieration of the greater thickness of the layers on a younger 

 tree? The only direct data I possess bearing on this point are derived 

 from a piece of a transverse section, 3| inches deep, of a ' rail,' which the 

 exhibitor says was taken from the trunk at the height of 275 feet from the 

 ground. As its layers, on a breadth of nearly |ths of an inch, show only a 

 slight curvature, it must have come from a part of the trunk still several 

 feet in diameter. On this section, the exterior inch, nearly all alburnum, 

 contains 90 layers, the next 60, the next 45, the remaining half-inch 1(5, 

 making 32 to the inch. That the exterior layers should be thinner at this 

 height than more near the base of the tree, is just what would be expected. 

 If we apply this ratio of decrease of the number of layers to the inch as we 

 proceed inwards to the section of 25 feet from the ground, we should, at 

 4 inches within that part of the circumference which I have examined, have 

 only seventeen layers to the inch, which, taken as the average thickness, 

 would make the tree only 1034 + 24 = 1058 years old. But it is not pro- 

 bable that the thickness of the layers increases so rapidly. The data we 

 ])ossess on other trees go to show that a tree, after it is 400 or 500 years 

 old, increases in diameter at a pretty uniform rate for each twenty addi- 

 tional years, on the whole, although the difference of the thickness of any 

 two or more contiguous layers, or the same layer in different parts of the 

 circumference, is often very great. Still, when we consider how very much 

 thicker are the annual layers of a vigorous young tree than of an old one, 

 perhaps we should not be warranted in assuming more than the average of 

 seventeen layers to the inch for the whole section. Some useful data may 

 be obtained from a tree more nearly related than any other to those of 

 California, though of a different genus, namely the so-called Cypress of our 

 Southern States (Taxodium distichum, Rich.). I possess three sections of 

 different trees of Taxodium, reaching from the centre to the circumference. 



