204 Dr. W. C. Williamson. On the Organisation [Mar. 13, 



Observations, &c. (continued). 



Washington : — U.S. Department of Agriculture. Bulletin. No. 1. 

 8vo. Washington 1889 ; North American Fauna. Nos. 1-2. 

 8vo. Washington 1889. The Department. 



U.S. Geological Survey. Bulletin. Nos. 48-53. 8vo. Washing- 

 ton 1888-89 ; Monographs. Vols. XIII-XIV. 4to. Washing- 

 ton 1888. The Survey. 



March 13, 1890. 



Sir HENRY E. ROSCOE, Knt., Yice-President, in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Papers were read : — 



I. "On the Organisation of the Fossil Plants of the Coal- 

 measures. Part XVII." By William Crawford William- 

 son, LL.D., F.R.S., Professor of Botany in the Owens 

 College, Manchester. Received February 8, 1890. 



(Abstract.) 



In 1873 the author described in the 'Phil. Trans.' an interesting 

 stem of a plant from the Lower Carboniferous beds of Lancashire, 

 under the name of Lyginodendron Oldhaminm. He also called 

 attention to some petioles of ferns, more fully described in 1874 

 under the name of Bachiopteris aspera. The former of these plants 

 possessed a highly organised, exogenously developed, xylem zone, 

 whilst Bachiopteris was only supplied with what looked like 

 closed bundles. Since the dates referred to, a large amount of 

 additional information has been obtained respecting both these 

 plants. Structures, either not seen, or at least ill-preserved, have 

 now been discovered, throwing fresh light on their affinities ; but 

 most important of all is the proof that the Bachiopteris aspera is 

 now completely identified as the foliar rachis or petiole of the Lygino- 

 dendron ; hence there is no longer room for doubting that, notwith- 

 standing its indisputable possession of an exogenous vascular zone, 

 the bundles of which exhibit both xylem and phloem elements, along 

 with medullary and phloem rays, it has been a true Fern. Though 

 such exogenous developments have now been long known to exist 

 amongst the Calamitean and Lycopodiaceous Ferns, as well as in 



