XXIX] LAGENOSTOMA 55 



and others have shed their contents by the splitting of the thin 

 inner walls of the loculi. The sporangial walls are composed of an 

 outer layer of large cells with dark contents succeeded by 2 3 

 layers of smaller and crushed cells. The spores, 5 6 JJL x 3-5 4 p, 

 in diameter, have a reticulately sculptured exine: Dr Benson 1 

 states that they agree closely with pollen-grains found in the 

 pollen-chamber of Lagenostoma ovoides except in their slightly 

 smaller size ; she notes the association of Telangium with fragments 

 of the vegetative organs of Lyginopteris and draws attention 

 to resemblances in the structure of the tissues; but the most 

 interesting comparison, at least in an academic sense, is with the 

 seed Lagenostoma, the integumented megasporangium of Lyginop- 

 teris. Dr Benson points out that a transverse section of a Lageno- 

 stoma in the plane of the canopy, showing the nucellar apex 

 surrounded by radially disposed chambers (fig. 409), presents a 

 certain resemblance to a synangium of Telangium Scotti; and 

 it is suggested that the chambers encircling the nucellus may 

 represent sterilised sister-sporangia 2 . ' The seed in fact is assumed 

 to be a synangium in which all but one of the sporangia are sterile, 

 and form an integument to the one fertile sporangium which has 

 become a megasporangium with one large megaspore.' This 

 view, though clearly incapable of confirmation in the present 

 state of our knowledge, is not merely an ingenious hypothesis but 

 a stimulating suggestion as to possible homologies : as an argument 

 in favour of associating Lagenostoma and Telangium as the spore- 

 bearing organs of the same plant it has but little weight. 



iv. The Seed. Lagenostoma Williamson. 

 Lagenostoma Lomaxi, Oliver and Scott ex Williamson, MS. 



In 1877 Williamson 3 proposed the generic name Lagenostoma 

 for some petrified seeds from the Lower Coal Measures of Lanca- 

 shire and described two species, Lagenostoma ovoides and L. 

 physoides: in his MS. Catalogue a third type is referred to as 

 Lagenostoma Lomaxi. It is this third type that Prof. Oliver 



1 Benson (04) B. 



2 In his account of the ovule of Stangeria Lang (00) discusses the possibility 

 of homologising the ovule with a sorus consisting of one sporangium. 



3 Williamson (77) B. p. 234. 



