Traumatic Ray-Tracheids in Cunninghamia sinensis. 1 
BY 
EDWARD C. JEFFREY, 
Professor of Plant Morphology , Harvard University . 
With Plate XXXI. 
I T is usual at the present time among perhaps the greater number of 
botanists to regard the Coniferales as an ascending series, beginning 
with the Taxineae,as relatively the most primitive, and passing through the 
Cupressineae and Taxodineae to the Abietineae, the most highly specialized 
and modern. This view is. based on the greater simplicity of structure of 
the first-named tribe and the more complex organization of the latter. Yet 
there is practically nothing in the palaeobotanical evidence which really 
gives it support. Moreover, it is beginning to be realized that apparent 
simplicity of structure is by no means a reliable criterion of greater 
antiquity. In fact, quite the opposite conclusion more often results from 
the consideration of the extinct older forms. For example, the Calamites 
were infinitely more complicated in both their reproductive and vegetative 
structures than is their living survivor, the genus Equisetum . Similarly, 
the organization of the Lepidodendroids was very much more elaborate than 
is that of any of the existing representatives of the Lycopodinean stock. 
The study of reversions, especially of those which are susceptible of 
experimental treatment, has become of increasing importance in mor- 
phology, for if in a presumably more ancient, because more simply 
organized group, it can be shown that reversions to a type of structure 
possessed by a more complicated related group may be experimentally 
produced, it becomes at once extremely probable that the more highly 
organized forms are the more ancient. This conclusion becomes a certainty 
if it is supported by a considerable body of collateral evidence, especially 
if such evidence is derived from the study of extinct forms. 
The complicated structure of the medullary rays in the existing 
Abietineae, composed of both parenchyma-cells and so-called ray-tracheids, 
as well as the very elaborate system of ligneous resin-canals found in the 
tribe, are considered by many as evidence of extreme specialization and 
1 Contributions from the Phanerogamic Laboratories of Harvard University, No. 13. 
[Annals of Botany, Vol. XXII. No. LXXXVIII. October, 1908.] 
