1916] JEFFREY & TORREY—GINKGO 287 
those of the Abietineae, and having the same relations to the 
similar internal structures as do those in Pinus or Abies. The 
possession of short shoots and the opposite pitting of the secondary 
wood, bars of Sanio, etc., as well as a number of other character- 
istics, likewise definitely indicate a closer degree of relationship 
between the Abietineae and the Ginkgoales than exists between 
the latter and any other gymnospermous group. It is accordingly 
of great interest and importance in the present connection to dis- 
cover that in so many particulars there is the same striking agree- 
ment in the organization of the mechanical apparatus of the 
microsporangium in the Abietineae and the sole surviving genus 
Ginkgo. One of us has pointed out® that on cogent grounds the 
Abietineae may be divided into two subsidiary groups, the Abie- 
teae and the Pineae. The former are without resin canals in the 
secondary wood, while the latter are provided with ligneous ducts 
and have an organization of root, leaf, and cone in contrast to that 
of similar structures in the Abieteae. A further feature of distinc- 
tion between the Abieteae and the Pineae is the thick wall of the 
Sporangium in the former. The greater thickness of the wall of 
the microsporangium of the Abieteae makes it more favorable for 
study than that of the Pineae. Fig. 12 illustrates the organization 
of the wall of the sporangium in the genus Pseudolarix, which, on 
account of the absence of tanniniferous contents in the cells of the 
sporangium wall, is the most suitable for illustration. It is clear 
that the mechanical tissues in this case, as in Ginkgo, extend to the 
cavity of the sporangium. The outward limit of the opening 
mechanism in this instance is the exterior of the spore sac and 
not, as in Ginkgo, the layer immediately under the epidermis. 
The same general situation obtains in all the conifers, apparently, 
for throughout the group the epidermal cells have the same organi- 
zation as the mechanical elements. Fig. 1o reproduces a part of a 
vertical section of a sporangium of Pseudolarix. On the left of the 
figure lie certain cells which have reticulated walls. These are the 
transfusion elements, and further in toward the axis they are 
joined with the tracheids of the single fibrovascular bundle of the 
* Jer j ee Cy. Phe cage anatomy of the Abietineae. Mem. Boston 
Soc. Nat, "Hist, 6:1-37. pls. 1-7. 
