14 PROCEEDINGS OF THE ACADEMY OF [1884, 



if we could find them, supposed to be absolute, we now look upon 

 allied species as haA'ing descended from a common ancient stock, 

 of which intermediate forms have died out, and therefore do not 

 expect that allied forms, on the whole distinct and definable, 

 should be completely unconnected by certain links or vestiges of 

 links. Moreover, it used to be thought that hybrids were neces- 

 sarily sterile, but it is now known that some hj'brids are fertile, 

 and that their offspring, fertilized b}'^ either parent, are generally 

 fertile ; that in this way intermediate forms between two species 

 may originate ; and it is clear that the two species ought not to 

 be reduced to one on account of such intermediate forms. Dr. 

 Gray referred to Rosa, Biibus and Hieraciwrn , in the Old World, 

 as genera in which no two botanists who had studied them could 

 agree as to what were species ; one school reducing them to very 

 few, which they can define only by disregarding certain interme- 

 diate forms ; the other multiplying them by hundreds, and char- 

 acterizing them by distinctions which might serve for the speci- 

 mens in hand, but which failed with every new collection. This 

 necessitated either the formation of a still finer-drawn set of species, 

 or the falling back to the broader Linnsean conception of a species. 

 The latter alternative had been generally followed in this country, 

 and Dr. Gray hoped that the coming American botanists would 

 incline to this view in the treatment of our critical genera. 



Relation of Iledidlary Rays to the Strength of Timbei\ — Dr. 

 RoTHROCK called attention to some experiments made by Mr. 

 Frank Day, in the laboratoiy of the University of Penna.,on the 

 relation of the medullary ray to the strength of timber. Mr. 

 Day had found that it required just about twice as much force 

 (say 1130 pounds) to pull apart a square inch of live oak, if 

 the force ran parallel to these ra3's as if the force were applied 

 at right-angles to them. 



What is true of the live oak was also largely true of other 

 timbers. The buttonwood (Platanvs occidentalis) was remark- 

 able for the development of its medullary rays, and also for the 

 difficulty in splitting that wood at right-angles to them. 



Mr. Day's experiments also proved that there existed great 

 differences in the quality of the material of the woody fibre ; for 

 in timber where the relative proportion of wood and ducts could 

 well be compared, and where the fibres were of equal size through- 

 out, differences in strength were to be found. 



Botanical Notes. Double Floicers in Gelsemium nitidum; 

 Euonymus Japonicvs ; Development of Fruit of Opuntia ; Helian- 

 thus tuberosus; Garya glabra. — Mr. Meehan exhibited two speci- 

 mens of double flowers of Gelsemium nitidum, one found wild 

 in Georgia, the other in Alabama. One was straw-colored, the 

 other deep yellow. He remarked that many double flowers in 



