NATURAL SCIENCES OF PHILADELPHIA. 141 



within the last three or four years pushed out on trees which had evidently 

 once borne only female ones; but in no instance did a female branch start 

 out from a male tree. Having once began to bear male flowers, these 

 branches continued to develop these only, presenting the appearance of an- 

 other variety grafted on another stock. 



Returning to Philadelphia, noting every tree I met on the side walks, I saw 

 a very few trees which had male and female flowers scattered promiscuously 

 over the same branches. These are very rare; but the fact of their existence 

 may have an important bearing on any attempt to evolve the laws governing 

 the production of separate sexes. 



At Germantown I chose for the field of my investigation the large estate of 

 Mrs. G. W. Carpenter, on which are many hundreds about twenty-five to 

 thirty years old ; but amongst all these I did not note one which showed any 

 tendency to branch into distinct sexes like those at Bristol, or any one with 

 mixed sexes like the few seen in Philadelphia. All the trees were either ex- 

 clusively male, or exclusively female. 



The parts of fructification in Acer dasycarpum have no^, to my knowledge, 

 been minutel}^ described. It will be of interest, in connection with the sub- 

 ject of this paper, to note them. 



There are three classes of buds on the tree : leaf-bearing, staminate. and 

 pistillate. The leaf-bearing buds are formed of eight imbricated scales in four 

 pairs, the scales all distinct and beneath the uppermost pair ; five embryo 

 leaves, rolled up to look very much like imperfect anthers, form a sort of 

 crown. The bud bearing the staminate flower, or rather which forms it, 

 has also eight scales, the upper two uniting for nearly half their length, and 

 recurved at their summits when the flower is fully formed, making a cup-like 

 involucre, at the bottom of which arise five (rarely seven) corollas, which are 

 separated from each other at their bases by a fuscous down. These corollas 

 are about one-fourth o-f an inch long, the lower half tubular, the upper half 

 funnel-shaped, the five (rarely seven) stamens arising from the base of the 

 funnel. The filaments are double the length of the corolla, which we may 

 properly term it. 



The female flower primarily resembles the other two in this, that it is com- 

 posed of eight scales imbricated in pairs ; but what in the male we call a 

 corolla is reduced to a pair ot united scales not more than one-thirty-secoud 

 of an inch in depth, united into a flattened cup, with the edges rather in- 

 clined than to turn out. In the center is the two-styled ovary, and at its 

 base arise seven stamens, although sometimes only four, generally five, push 

 their anthers above the minute scaly cup outside. These anthers appear 

 large and well-developed, but I have failed to find pollen in any one, and in 

 no instance have I been able to find a perfect stamen like unto those formed 

 in the staminate flower. These rudimentary stamens never push beyond the 

 scales. Though classed as a Polygamous species by authors, it would appear 

 from these observations a monoeciously Dioecious plant. 



In trying to classify my observations, in order to evolve some sexual law, 

 I found that vigor made no diflFerence ; weak trees or weak branches were 

 alike male or female Some individuals are more years coming into flower 

 than others. I fancied I had once got a clue in the fact that in the com- 

 mencement of my observations I found numerous specimens of great size 

 which were apparently commencing their fruiting age, and which were female 

 trees in all cases; but at length I discovered two trees of the same character 

 of the masculine kind. 



The only positive fact in relation to the matter seems to be that the sexual 

 character of the maple is not unchangable after the infancy of the tree ; and 

 that the tendency of development is from female to male. 



1868.] 



