204 THE POPULAR SCIENCE MONTHLY. 



anatomy, of embryology, and of geographical distribution would be 

 enough to satisfy us that the living things known to us are the 

 divergent descendants of more generalized ancestors, and that their 

 relationships can be most exactly expressed by a system of con- 

 verging lines, which meet and form larger branches to represent the 

 extinct ancestors from which our divergent species are descended. 

 The evidence is circumstantial, and only leads to general conclusions, 

 and a complete series of fossil forms is the only absolute proof which 

 we could have ; but, in the absence of this proof, the conclusions drawn 

 from the study of living animals are rendered extremely probable by 

 the fact that the fossil members of the more modern groups of ani- 

 mals, such as the mammals and birds, are just such forms as the 

 evidence from other sources leads us to expect, and the attempt to 

 read and interpret such records as we have, and to trace the history 

 of life with as much accuracy as possible, is therefore perfectly legiti- 

 mate, and may fairly claim the attention of the morphologist. 



-+*- 



ANNUAL GROWTH OF TREES. 



By A. L. CHILD, M. D. 



ARE the concentric rings of a tree a reliable record of its age in 

 years ? Such has been the conception in fact, the undisputed 

 knowledge of the world, for all time past. I have no recollection of 

 ever having seen or heard the authority of this record disputed till 

 Desire Charnay, in his " Ruins of Central America," said, when speak- 

 ing of the age of the ruins as proved by such a record : " Unfortu- 

 nately for the argument, it is altogether fallacious and proves nothing. 

 I have put the evidence to a test. On examining a slice of wood of 

 a shrub that I knew as a fact was only eighteen months old, I found 

 that it had eighteen concentric rings. I thought it was an anomaly, 

 but, in order to convince myself, I experimented upon trees of all kinds 

 and sizes, and invariably found the like result produced in very nearly 

 like proportions." * 



M. Charnay's statement was, in my estimation, rather loose, and 

 lacking in the proof of his absolute knowledge of the age of the trees 

 examined ; and again, so far as applicable to the case, was only so in 

 a tropical climate, where the conditions were entirely different from 

 those surrounding us in a higher latitude, and altogether raised but 

 little doubt on the subject. 



In April of 1871 I planted a quantity of the seed of the common 

 red maple {Acer rubrum). In transplanting, in 1873, they were 

 placed too near each other, and it has become necessary to cut a part 



* "North American Review," September, 1881, p. 401. 



