152 G. R. Wieland — American Fossil Gycads. 



apical lobes of a small central seed and there undergoing 

 prothallial growth, such an interpretation is, because of the 

 peculiar spindle-shaped and possibly ovulate base, not easily 

 dismissed. Should this prove to be the true interpretation of 

 Codonotheca, it is the most leafy of known seeds. But any one 

 is free to work out various alternative interpretations for him- 

 self. And certainly this singular fruit would be at once 

 explained by many, or most, as some entirely primitive form 

 of giant microspore case had not the ubiquitous staminate 



Fig. 9. 



Fig. 9. Cycadeoideu Macbridei (?). 



Diagrammatic reconstruction of the dicotyledonous embryo showing 

 approximate position of the bifurcation of the node (&/) and the probable 

 bundle distribution in the cotyledons. The two branches leading into the 

 cotyledons must run parallel further than here appears because the laminae 

 are shown as if arbitrarily flattened out. 



disks of Mesozoic times led us to expect to find circular 

 emplacements of sporophylls in process of reduction in ancient 

 plants, and in particular taught us to see, that in such disks 

 spores once borne ventrally may easily become falsely dorsal. 

 In any case, however, the study of such forms must ultimately 

 shed much light on the nature of gymnospermous testal 

 structure, the essential and primitive elements of which already 

 begin to appear. 



But yet another comparison of the seeds of Cycadeoidea 

 may be made with forms far nearer at hand that might have 

 been thought of before. Through the great kindness of Pro- 

 fessor R. B. Thomson, whose excellent demonstration of the 

 megaspore membrane of the gymnosperms is well known. I 

 have come into possession of a beautiful though limited series 

 of longitudinal sections of existing gymnospermous seeds ; and 

 the attentive study of these shows that the smaller seeds, espe- 

 cially of the Abietinea? present a clear analogy to Cycadeoidea 

 in all that pertains to lateral wall structure. In Pinus resinosa 



