Cunningham ia sinensis. 60 1 
it must have been at the earliest in the very late Cretaceous or the early 
Tertiary after the Abietineae had developed both ligneous resin- canals and 
marginal ray-tracheids. The structure of the female cone in the three 
tribes under discussion quite favours this view. In the Abietineae the 
megasporangiate cone is made up of pairs of superimposed scales with 
oppositely oriented fibrovascular systems. The female cones of the Taxodi- 
neae and Cupressineae are made up of single scales, but these contain 
a double system of fibrovascular bundles oriented as are those of the two 
distinct scales of the Abietineae. The conditions observed suggest naturally 
that in the Taxodineae and Cupressineae we find the fusion of two organs, 
which are still free in the more primitive Abietineae. A consideration 
of the gametophytic structure in the tribes under discussion apparently 
leads to a concordant conclusion, for we find both the microgametic and 
megagametic conditions much more simplified in the Taxodineae and 
Cupressineae than they are in the Abietineae. 
Summary. 
1. Marginal ray-tracheids, similar to those characteristic of the Abieti- 
neae are sometimes present in Cunninghamia. 
2. In Cunninghamia the ray-tracheids are traumatic in their origin and 
are most numerous in the region of the injured annual rings diametrically 
opposite to the wound-callus. 
3. The ray-tracheids of Cunninghamia present a general resemblance 
to those described by De Bary, Penhallow, and Gothan, in the Taxodineous 
or Cupressineous genera, Sciadopitys , Sequoia , Cupressus , Juniperus , and 
Thuya . 
4. The ray-tracheids in the genera mentioned constitute additional 
evidence for the derivation of the Taxodineae and Cupressineae from the 
Abietineae, and on this hypothesis are to be regarded as vestigial or 
reversionary. 
5. All the evidence goes to show that the Taxodineae and Cupres- 
sineae did not exist before the very end of the Cretaceous or more probably 
before the beginning of the Tertiary. 
It gives me much pleasure to offer my thanks to the Director of the 
Royal Gardens, Kew, and to my friend Mr. L. A. Boodle of the Jodrell 
Laboratory, Kew, for material secured there on a visit to England two 
years ago. 
