1916] JEFFREY & TORREY—GINKGO 289 
to their sporangial mechanisms, as in so many other features, show 
themselves more nearly related to the Ginkgoales and consequently 
to the Cordaitales. In the Gnetales the opening mechanisms of 
the sporangia likewise are much simplified and in this respect 
correspond to the higher subtribes of the Coniferales. 
In the highest of the seed-bearing plants, the angiosperms, the 
microsporangium characteristically opens through the agency of 
an internal fibrous layer, which has been elaborately described 
in the monumental memoir of CHatin on the anatomy of the 
anther. In both the dicotyledons and monocotyledons this layer 
is, typically at least, well developed, but does not, as in the conifers, 
extend into the epidermis. Fig. 19 shows the organization of one 
of the loculaments of the anther in the common garden tulip 
(Tulipa Gesneriana, hybrid?). Toward the top of the figure lies 
the stomium, meeting with a corresponding structure belonging 
to the other loculament of the anther on the same side of the con- 
nective. The remainder of the wall shows the mechanical layer 
Strongly developed. In the epidermis stomata can be distinguished. 
Clearly there is no relation between the mechanical layer and the 
fibrovascular layer in the connective. 
Turning our attention now to the dicotyledons, in fig. 20 we 
find a diagrammatic representation of a loculament of the anther 
of Diervilla florida, the bush honeysuckle. The stomium does not 
appear in the figure, but the mechanical or fibrous layer of the 
anther is clearly to be seen, and, like that in the tulip, it does not 
extend into the epidermis. In this case, as in the other angiosper- 
mous sporangium figured, there is no connection between the 
mechanical tissues and the fibrovascular bundle of the micro- 
sporophyll. On account of the unique development of transfusion 
tissue of a gymnospermous character in the genus Casuarina, it 
seemed possible that there might be here, if anywhere, some con- 
nection between the mechanical tissues of the microsporangium 
and the fibrovascular bundles. Investigation of the stamens of 
two species of the genus, however, revealed the same general 
situation as is found in other instances among the angiosperms; 
namely, the absence of a relation of continuity between the reticu- 
lated cells of the sporangial mechanism and the fibrovascular 
