12 Watson, Tlie Cone of BotJirodeiidron innnduni. 



The isolated male sporophylLs may be separated by 

 the following characters* : — - 



1. The Bothrodendron sporophylls do not terminate in 



the characteristic lamina, only one cell thick, of 

 Miadesmia inembranacea, Bertrand. 



2. In Bothrodendron there is a great development of 



transfusion tissue in the sporophyll, particularly 

 round the base of the ligule : in the true 

 JSIiadesniia there is little or none. 



3. The vascular bundle in Bothrodendro)i is continued 



in the lamina up to the level of the top of the 

 sporangium ; in Miadesmia it stops sooner. 



4. The tip of the ligule is normally rounded in the 



sporophylls o{ Bothrodendron. I understand from 

 Miss Benson that in Miadesmia the tip of the 

 ligule is "lamellar." [Letter, August 24th, 1907.] 



Taken as a whole, the cone of Bothrodendron differs 

 essentially from that of Bliadesmia in the following 

 respects : — 



In Bothrodendron the megasporangium contains four 

 functional megaspores and is not surrounded by an integu- 

 ment ; in Miadesmia the sporangium contains only one 

 megaspore and is surrounded by a highly specialised 

 integument. 



The idea occurred to me that Miadesmia and Bothro- 

 dendron might be connected as are Lepidoearpon and 

 Lepidostrohus, but the great differences in stem structure 



* I have been unable to compare the sporophylls of Botlirodendron wilh 

 those of Miadesmia in much detail owing to the fact that my knowledge of 

 Miadesmia is derived entirely from the poor preparations in the Manchester 

 collections. I look forward to the forthcoming monograph, by Miss Benson, 

 on Miadesmia to reveal many oth<ir points of difference and clear up all the 

 confusion which has arisen. 



