350 THE ANATOMY OF WOODY PLANTS 



found in Pityoxylon. This is, for example, true in the case of 

 the genus Sequoia, which, on the basis of general anatomical 

 principles, obviously formerly possessed both the ligneous resin 

 canals and the marginal ray-tracheids of the older Abietineae. 

 Examples might be indefinitely multiplied to show that the use 

 of the mature structure of the wood in the Coniferales, without 

 recourse to comparative anatomical and experimental data, is 

 almost certain to lead in a given case to fallacious conclusions. 



It is now possible to sum up the situation from the standpoint 

 of evolutionary anatomy for the phylogenetic sequence. It will 

 be convenient to indicate preliminarily that the most generally 

 accepted hypothesis of the morphological nature of the ovuliferous 

 cone in the Coniferales furnishes a prima facie argument in favor 

 of the primitive position of the Abietineae. In this subtribe the 

 female cone consists of pairs of scales, the upper of which is ovulif- 

 erous and the lower sterile. The ovuliferous scale is with a strong 

 degree of probability to be regarded as a persistent single sporophyll 

 bearing two seeds or megasporangia on its morphologically lower 

 but physically upper surface. The megasporophyll is in relation 

 to the abortive axis of the reproductive short-shoot. Aside from 

 the morphological interpretation of the structures concerned, 

 however, the fact remains that the units of structure in the ovulif- 

 erous cone of the Abietineae are double and separate in their 

 nature. In the female cones of the remaining coniferous sub- 

 tribes there is clear evidence from comparative anatomy of the 

 presence of fused pairs of scales in the ovuliferous structures. 

 In accordance with general principles of morphology and without 

 necessarily accepting the hypothesis of the short-shoot nature 

 of the vertically paired scales of the abietineous cones, it is probable 

 that the Abietineae are an older group than are the remaining 

 coniferous sub tribes. 



An additional argument for the antiquity of the Abietineae 

 is furnished by their obviously close relationship to the Ginkgoales, 

 which are admitted on every hand to be a primitive group of 

 gymnosperms. The affinity with the Ginkgoales shows itself 

 in the common possession of vegetative short-shoots by both the 

 sole surviving Ginkgo and by the ancient but still prolific genus 



