J2 Dr. W. C. Williamson on 



Sporangia; an apparently distinct form. 



p. 220, like Fig. 25, C.N. 1879. Cells of Sporangial \yall 

 much smaller. See C.N. 319a and 318. 



Several sporangia like Fig. 25, C.N. 318. 



Several sporangia, one evidently pendunculate, C.N.319. 



MYELOPTERIS. Renault. MYELOXYLON. Brongniart. 



Few fossil plants have been the subjects of more con- 

 troversy than those figured in my Memoir under the first of 

 the above names. The Medullosa of Cotta, the Palmacites 

 of Corda, the Stenzelia of Gceppert, to the two names at 

 the head of this paragraph, including the new Rachiopteris 

 Williamsoni of Seward, — this group has not only received 

 a confusing number of names, but the question of its 

 position in the vegetable kingdom has led to its being 

 tossed to and fro between the Cycads and the Ferns. In my 

 Memoir referred to above, I described a series of specimens 

 in my Cabinet, numbered from C.N. 276 to 305. M. Renault 

 at the same time was, unknown to me, studying similar 

 objects ; we finally and independently arrived at the same 

 conclusion, viz., that they were Carboniferous representa- 

 tions of the living group of Marattiaceous ferns. At a later 

 period my old pupil, Mr. Seward, undertook a re-examina- 

 tion of my specimens, and found amongst them what 

 appeared to be examples of two different forms. One of 

 these he regarded as being true Myeloxylons, and the 

 others as belonging to a more ordinary type of ferns, 

 which he determined to publish under the name of 

 Rachiopteris Williamsoni. The first result was the publica- 

 tion, in the Annals of Botany, for March, 1893, of a memoir 

 on the Myeloxylons, which he regarded as constituting an 

 independent type of plants intermediate between the Ferns 

 and the Cycads, but apparently having a nearer relation to 

 the latter than to the former family. 



Under these circumstances, in reply to my request, he 



