PAST HISTORIES OF PLANT FAMILIES 89 



sible, to say which is the highest, the most evolved type. 

 In the consideration of the Gymnosperm family it is 

 brought home with great emphasis how incomplete and 

 partial our knowledge is as yet. Many hold that the 

 Araucarecs are the most primitive of the higher Gymno- 

 sperms. In support of this view the following facts are 

 noted. They have a simple type of fructification, with 

 a single seed on a simple scale, and many scales arranged 

 round an axis to form a cone. In the microscopic struc- 

 ture of their wood they have double rows of bordered 

 pits, a kind of wood cell which comes closer to the old 

 fossil types than does the wood of any of the other living 

 genera. Further than this, wood which is almost indis- 

 tinguishable from the wood of recent Araucarias is found 

 very far back in the rocks, while their leaves are broad 

 and simple, and attached directly to the stem in a way 

 similar to the leaves of the fossil Cordaitece, and very 

 different from the needle leaves on the secondary stems 

 ■of the Pine family; so that there appears good ground 

 for considering the group an ancient and probably a 

 primitive one,^ 



On the other hand, there are not wanting scientists 

 who consider the Abietinece the living representatives of 

 the most primitive and ancient stock, though on the 

 whole the evidence seems to indicate more clearly that 

 the Pine-tree group is specialized and highly modified. 

 Their double series of foliage leaves, their complex cones 

 (whose structures are not yet fully understood), and their 

 wood all support the latter view. 



Some, again, consider the Taxecz as a very primitive 

 group, and would place them near the Cordaiteae, with 

 which they may be related. Their fleshy seeds, growing 

 not in cones but on short special axes, support this view, 

 ■and it is certainly true that in many ways the large seeds, 

 with their succulent coats and big endosperm, are much 



' From the Cretaceous deposits of North America several fossil forms (Brachy- 

 Jihyllum, Protodammard) are described which show clear affinities with the family 

 as it is now constituted. (See Hollick and Jeffrey; reference in the Appendix.) 



