298 F. O. BOWER. 



vascular bundles enter the stem from the leaves of Gnetum, 

 while from those of Welwitschia (at all events from the 

 cotyledons and young plumular leaves) and Ephedra the 

 number is two. 



In the hypocotyledonary stem the bundle system 

 resembles that of Pinus pinea (* Conif. und Gnet./ p. 

 26^-7), there being a comparatively large number of separate 

 bundles^ which do not rotate in the hypocotyledonary stem, 

 while the bundle sheath does not appear till the point of 

 transition from stem to root. At this point the xylem of 

 only two of the bundles rotates on its axis, while the 

 phloem of each of these divides into two parts, which 

 mutually fuse to form the primary phloem of the root. 

 The rest of the bundles pursue a direct course downwards, 

 and are lost in the cambium of the root. 



In the minute structure of the tissues the three genera 

 are known to have many characters in common. In Gnetum, 

 however, laticiferous tissues are present in considerable 

 quantity; in this property it stands apart from the other 

 members of the group. 



Taking into consideration all the characters above de- 

 scribed, the general result of this investigation is to show 

 that the group of the Gnetacese is a still more natural one 

 than it has hitherto been known to be : though the three 

 genera do not correspond very closely to one another in the 

 first cell divisions in the embryo, still the older seedlings show 

 many points of remarkable similarity both in external form 

 and internal structure. Further, it will be seen that 

 G. Gnemon is in reality but little more closely comparable 

 with the Angiosperms than the other two genera. In the de- 

 velopment of its embryo it obviously follows the type of the 

 Coniferse, and indeed approaches them in some respects 

 more nearly than either Ephedra or Welwitschia. 



