THE GYMNOSPERMAE : CONIFERALES AND TAXALES 677 



the bract scale from view. The outer surface of the cone consists of the 

 rhomboidal ends of the ovuHferous scales, each with a small central pomt 



or umbo. , 1 • , 1 rj.. 



This double structure has long been a morphological puzzle. ihe 

 ovuliferous scale is supplied by a vascular trace which arises quite inde- 

 pendently from that of the bract scale, and it is held by most botanists to be 

 axillary to the bract scale and therefore a branch or part of a branch. If the 

 bract scale is homologous with a scale leaf of the vegetative shoots, then the 



Ovuliferous scale 

 Bract scale 





I\V. » ,1 f . 



Ovule 



, Cone axis 





pi(. 677.— P^«'s svhestris. Longitudinal 

 section of a young female cone at the 

 pollination stage early m its first year. 

 Note that the scales are well separated, 

 thus admitting the microspores. 



ovuliferous scale must be homologous with a modified leaf spur. Its vascular 

 structure, however, is rather that of a leaf than an axis , ■ . •, 



The lassical theory is that of Alexander Braun (1853), who exp amed 

 as equivalent to the two leaves of a leaf spur, each beanng an ovule on it 

 ventral (abaxial) surface, which have become united by the.r upper (an ter or) 

 margins This would bring the vemral surfaces uppermost as shown m the 

 diagram (Fig. 678), which illustrates the supposed course of evolution^ The 

 Srfinds support in the inverted position of the vascu ar bundles of 

 the sLe (xvlems downwards) and in the development of the ' double ea 



n th Cup;essinean g.nus SciadopHys, in which the suggested fusion actu y 

 occurs during the development of each leaf. How much importance should 



be attached to the vascular structure is doubtful, as similar inverted bundles 



