394 PROCEEDINGS OF THE ACADEMY OF [1888. 



We now see that a plant may find itself in a climate or in sur- 

 roundings favorable to an early development of stamens ; in anoth- 

 er case in a locality or country where the reverse will prevail. 

 Dichogamy will then vary. TVe also know that heredity plays a 

 j^art in fixing a constantly recurring local tendency, so that a plant 

 having acquired a tendency to proterandy or it may be to proter- 

 ogyny, would continue to carry the habit long after the superinduc- 

 ing causes had passed away. Plants remaining for ages in a local- 

 ity where the conditions Avould be favorable to a wide difference 

 between simultaneity, would probably become in time monoecious 

 or dioecious, and all this, as we see, from no particular assurance 

 that cross-fertilization would thereby be affected. 



In trying to reach generalizations of this character, we should 

 not, however, forget that in nature, things seldom follow from a 

 single cause, but from the operation of united forces. In this con- 

 nection I have shown, (see Proceedings of the American Association 

 for the Advancement of Science, Salem, and subsequent meetings,) that 

 sex itself is largely influenced by the amount of nutrition available 

 when the primordial cell is fertilized. If sex itself may be influ- 

 enced by nutrition, the subsequent growth of its repi'esentative or- 

 gans may still further be influenced, which would introduce into 

 the consideration an additional element aside from temperature 

 alone. 



I have my own postulate as to the significance of dichogamy. 

 I rest here by the simple proposition that whatever its significance, 

 it arises from no effort innate to the plant itself, but from an outside 

 force that can have little interest in ci'oss-fertilization. 



(It is proper to say that an abstract of this paper was read before 

 the American Association for the Advancement oj Science, at Cleve- 

 land. See Botanical Gazette for September 1888.) 



Trientahs Americana, Pursh. There can be but little doubt that 

 Trientalis Americana grew freely over what is now the city and 

 county of Philadelphia. It is still found in adjoining counties, and 

 here and there are old botanists who remember having collected it 

 on the confines of the county ; but it is not included in Barton's 

 Flora, now over 60 years old, — nor in Darrach's Catalogue, or any 

 published list so far as I know. In an old chestnut wood at Chest- 

 nut Hill, my brother Joseph detected a small patch this summer, 

 that has evidently been there for ages, but overlooked, — and this 

 suggests some thoughts on its habits and past geographical record of 

 general interest. 



