720 THE AMi-Ric.\.\.\.\ rrR.\i.isr. [ \ ni.. xxxviii. 



a true sympodium. In comi)arniK this with tlie i-nonopodial 

 branch of vigorous growth, it appears thai ihc aUeralions in- 

 volve more than mere suppression. In the monoiMKlium the 

 average angle of divergence for the lateral nienil)crs is 4^.3°, 

 %vhile for the deiutd foini it is 341 [Ik nttu uill be >,een 

 to completely fulhll all conditions with respect to the develop- 

 ment of a phvlum, even to indicating tlic position ot missing 

 members. Selecting Irom this such ])ortion as mav serve the 

 requirements ol the present case, we obtain the lodowmg hgure 

 x\hRh mu Ik held to cmb xK <. u tin il coiuluMon. i. to the 

 gencid sac.e.sim ot the dilfe.^ it ^\ mn ).p. i ms. and tiom it 

 we may gather that the highest representative — Pmus — is the 

 terminal member m the mam line ot descent from the Cycado- 

 f^hce^ through I\)io\\l,m, while fiom such a cential Ime both 

 the Cordaitales and Ginkgoales have been given off as side Imes. 

 In the construction of this figure an attempt has been made to 

 show all normally developed buds (o) and their relative dimen- 

 sions ; atrophied buds (o), the position of which is recognizable ; 

 and atrojjhied branches ( / -) which are still visible, but it is 

 obvious that the figure does not show many members, all evi- 

 dent e of the foimer existence ot which has eompletelv dis- 

 ai)i)eared. 



The .neneial icsults ot these iiu Lsii^ations sci \ e to tontii m 

 m a very striking manner the probable monophyletic ongm ot 



