- s 



248 MORPHOLOGY OF GYMNOSPERMS 



In 1864, also, Oersted described (11) some remarkable cones, 

 in which the lowest bracts had the form of foliage leaves ; in the axils 

 of the next higher bracts were several scales as on a suppressed axis, 

 the two outermost being the largest and opposite; higher up the bracts 

 became gradually smaller and the axillary scales less numerous, but 

 the two outermost scales gradually increased in size and became 

 connate by their adaxial (posterior) margins, while rudimentary 

 ovules appeared at their base; and in the uppermost part, of the cone 

 the bract was reduced to its ordinary size, and the ovuliferous 

 scales had fused into a single large broad structure dentate or bifid 

 at apex. 



One of the simplest ex- 

 planations of these problem- 

 atical structures was that 

 proposed by Sachs (14) in 

 Fig. 273.—Araucariacxcclsa: longi- 1 868, and afterward more fully 



tudinal section of bract {b) and scale (s) elaborated by ElCHLER (19). 

 from cone shown in f^g. 272; natural size. ^j^^y claimed that the bract 



is a carpel, and the ovuliferous 

 scale a ligular outgrowth from its face, calling attention to a similar 

 condition in the leaves of Isoetes and Selaginella. Such a ligular 

 placenta does not appear among the Taxodineae and Cupressineae, 

 and in these cases the bract is evidently an open carpel. 



In 1869 Van Tieghem presented his conclusions (16) based upon 

 anatomical structure, a . new point of view. He states that the 

 bundles of the bract and of the ovuliferous scale leave the main axis 

 each in its own sheath, and therefore represent independent systems 

 of bundles and independent members; that the upper bundle divides 

 to form an arc (in transverse section) of bundles with inverse orien- 

 tation, the arc arrangement showing that the axillary structure is a 

 leaf and not a branch; and that the inverse orientation shows that the 

 leaf belongs upon the suppressed branch opposite the bract. His 

 conclusion was that the ovuliferous scale is the first and only leaf of 

 an axillary branch. 



In 1 87 1 Von Mohl further strengthened Braun's position by 

 the publication (17) of his studies of the peculiar "double leaf" of 

 Sciadopitys. He showed that this leaf represents the first two leaves 



