CORDAITEAE 553 



affinity with Ginkgoaceae, which in many respects also 

 hold an intermediate position between Cycadophyta 

 and Coniferae, appears the strongest from every point 

 of view. 



The comparison of the female inflorescence with 

 that of the Gnetaceae seems to rest on a very weak 

 basis. It is not proved beyond doubt that the 

 ovule of Cordaiteae had two integuments, still less is 

 there any indication that the two were of a different 

 morphological nature, as appears to be the case in 

 Gnetaceae. It is probable that the affinities of the 

 Gnetaceae may lie in quite a different direction, 

 namely, in that of the Mesozoic Bennettiteae (see 

 Chap. XIII.). 



The structure of the seeds which are known to 

 have belonged to Cordaiteae, is altogether Cycadean, 

 and, as we have seen, even minute details, such 

 as the form of the pollen -chamber, can be exactly 

 paralleled among recent Cycads. These facts, together 

 with the foliar structure, appear to prove conclusively 

 a real affinity between the two families, though in 

 other respects they diverged widely from one another. 

 But just in the points where there is a strong agree- 

 ment with Cycadaceae (with Bennettiteae the relation, 

 as regards the seed-structure, is much less close) the 

 Pteridosperms are likewise approached. The ana- 

 tomical characters, together with the seed-characters 

 and those of the multicellular pollen-grain, show such 

 manifest correspondence that there can scarcely be a 

 doubt that Cordaiteae sprang from the same stock 

 with Pteridosperms, though at a very remote period. 

 The characters which they share with the Cycadophyta 



