260 



The medulla in this case appeared to be wholly inactive. 



By an examination of buds which had been inserted in a preceding 

 summer, or attached by grafting in the spring, it appeared that ves- 

 sels diverged from them into the bark of the stock. 



It seems therefore probable, that a pulpous organizable mass first 

 derives its matter from the bark or alburnum, and that this matter 

 subsequently forms the new layer of bark ; for if the vessels had pro- 

 ceeded as radicles (according to Darwin's supposition,) from the 

 inserted buds or grafts, such vessels would be different from the 

 natural vessels of the stock ; neither is it probable that vessels could 

 extend, by actual addition to their extremities in the course of a few 

 days, from the leaves to the roots. Mr. Knight is consequently in- 

 clined to believe that the matter itself which composes the new bark 

 acquires an organization of vessels calculated to carry the true sap ; 

 but whether, in the ordinary growth of trees, this matter be derived 

 from the bark or the alburnum, or from both, it will be extremely 

 difficult to determine. This, however, is certain, that bark in many 

 cases exists previous to the existence of alburnum ; but there seems 

 to be no case, in the ordinary growth of vegetables, in which albur- 

 num exists previous to the formation of bark. 



An Investigation of the general Term of an important Series in the in- 

 verse Method of finite Differences. By the Rev. John Brinkley, 

 D.D. F.R.S. and Andrews Professor of Astronomy in the Univer- 

 sity of Dublin. Communicated by the Astronomer Royal. Read 

 February 26, 1807. [Phil. Trans. 1807, p. 114.] 



On Fairy -rings. By William Hyde WoUaston, M.D. Sec. R.S. 

 Read March 12, 1807. [Phil. Trans. 1807, p. 133.] 



In this paper the author relates briefly some observations which 

 he formerly made on the progressive changes of these rings, which 

 appear to him to lead to a satisfactory explanation of their origin. 



In the first place he observed, that some species of fungi were 

 always to be found at the exterior margin of the dark ring of grass 

 if examined at the proper season. This position of the fungi led him 

 to conjecture that progressive increase from a central point was the 

 probable mode of formation of the ring ; and he thought it likely 

 that the soil which had once contributed to the support of fungi, 

 might be so exhausted as to be rendered incapable of producing a 

 second crop. The defect of nutriment on one side would occasion 

 the new roots to extend themselves solely in the opposite direction, 

 and would cause the circle of fungi continually to proceed, by annual 

 enlargement, from the centre outwards. The luxuriance of the grass 

 follows as a natural consequence, as the soil of an interior circle is 

 enriched by the decayed roots of fungi of the succeeding year's growth. 

 Such a progressive enlargement, he remarks, had already been ob- 

 served by Dr. Hutton on the hill of Arthur's Seat near Edinburgh ; 

 but Dr. Hutton had not attended to the production of fungi. 



