12 PROCEEDINGS OF THE ACADEMY OF 



European species. American species. 



Cercis siliquastriuni. Cercis Canadensis. 



Celtis australis. Celtis occidentalis. 



Platanus orientalis. Platanus occidentalis. 



Acer platanoides. Acer saccharinum. 



Juglans regia. Juglans nigra. 



Crataegus oxyacantha. Crataegus cordata. 



In the Jirst of the points to which attention has been directed, the only ex- 

 ception appears to be in Larix Europwa, which drops its leaves at near the 

 same time as the American, and, unlike all the other species named, exhibits 

 in fading the same tinted leaves. 



In point 2. Fagus ferruginea has a more strongly toothed margin than the 

 European F. sylvatica ; but it is also worthy of note that the leaves of the 

 English species are more coriacious than the American, which may have 

 checked the prolongation of the nerves forming the teeth in the latter species. 

 If there is any difference in the consistency of the leaves, it is usually in favor 

 of the American species. 



In 3. Quercus cerris has smaller acorns than C. macrocarpa, but it is the 

 most distantly allied species brought into comparison. 



In 4. I know of no exceptions. 



In 5. In some few instances the buds of European species appear to be no 

 larger than the American, and in still fewer instances seem smaller ; but the 

 rule holds good so generally as to form a striking and prevailing character. 



It is proper to remark that the observations were taken from allied species 

 that I have been able to find growing in proximity to each other, and in as 

 similar circumstances as possible. This is very important, as, to a limited 

 extent, circumstances have an influence in the variation of characters. For 

 instance, Quercus alba, when growing in the full light and unsurrounded by 

 other trees, has its leaves much more deeply sinuated than when growing in 

 a mass with others. Lack of attention to this fact would make standard 

 botanical works in some instances seem to oppose the conclusions I have 

 arrived at. As an example of this, Michaux figures Fagus ferruginea with 

 larger fruit than F. sylvatica, and the leaves of Juglans regia as less serrulate 

 than those of J. nigra, neither of which agrees with my experience of plants 

 grown near each other in this climate, and is probably, if not altogether, an 

 error in drawing, to be accounted for by the supposition that the sketches 

 were made from specimens growing under widely diverging circumstances. 



The species employed in the comparisons are not in all cases the nearest 

 that might be had. Pyrus baccata, for instance, would be a better match for 

 P. coronaria than P. malus, but they were the best my facilities afforded me. 

 Some allied trees could not be compared in all points, and were therefore left 

 from the list. sEsculus, for instance, had shed its leaves at the date given, 

 too early for comparison in persistency of foliage ; but in points 2, 3, 4 and 5 

 the differences between JE. hippocastanum, on the European, and JE. ftava, on 

 the American side, agree with other species of the other genera named. 



The observations are perhaps too limited, in the absence of more extensive 

 examinations of other characters and other plants, to establish the fact that, 

 whatever may be the principle governing the origin of species, whether it be 

 by "progressive development," "natural selection of physiological advan- 

 tages," or by "special and continuous acts of creation," it is in conformity 

 with one regular and uniform law ; but their tendency is so evidently in that 

 direction, that I submit the facts for more general investigation, in the belief 

 that it will prove a novel and interesting branch of study in Botanical Science. 



[Jan. 



