OF ARTS AND SCIENCES. 



335 



of some of the great lights of English literature, comparing 

 the existence of each with the few inches of growth of the 

 tree, exhibiting in striking contrast the shortness of man's 

 earthly career. Some conversation ensued on the popular 

 notion that, under certain circumstances of external condi- 

 tion, more than one ring might be formed in a single year. 



Professor Gray regarded all such opinions as erroneous, or 

 at least not based on any reliable observations. So far as is 

 known, in temperate climates, all ordinary woods make one 

 annual ring ; the fact has not as yet been determined so 

 decidedly in the case of tropical trees. Young trees grow 

 more rapidly and unequally than old ones, and hence an ine- 

 quality in the width of the rings. 



Professor Agassiz said that Mr. H. J. Clark had recently 

 noticed that in the climbing Dogwood {Rhus Toxicodendron) 

 the side of the branches resting on any opposing object be- 

 comes thickened by an increased development of the rings 

 on that side. 



Professor Gray said he had observed this unequal growth 

 in the same plant in old stems of the plant, but had not 

 noticed it as bearing any relation to any circumstances of 

 position. Such anomalies are common in climbing plants, 

 particularly in those of southern and tropical climates. Mr. 

 Clark had shown him very young stems of Rhus, in which 

 the same irregularity existed without any reference to posi- 

 tion. The fact is, that, after the first year, the woody layer 

 fails to be formed on one side of the stem, and that too on the 

 free and convex side, not on that which is flattened by pres- 

 sure against the supporting object, as would have been ex- 

 pected. Mr. Clark has promised to investigate this anomalous 

 growth more particularly. 



Dr. B. A. Gould stated, that in Texas it had been pointed 

 out to him, that trees grow most on the south side ; and the 

 circumstance was depended upon at times by hunters to direct 

 their path. 



Professor Gray observed that such facts are well known, as 



