288 BOTANICAL GAZETTE [OCTOBER 
sporophyll. Toward the right and below in the figure the typical 
transfusion cells pass directly into elements with a more open 
reticulation of the wall, the mechanical cells, which constitute the 
opening mechanism of the sporangium. The jacket of active cells 
is complete on the free surfaces of the sporangium except where 
the stomium is present in a terminal position. The septum 
between the two spore sacs is very largely composed of the fiber 
cells and the transfusion elements with which they are joined. 
Fig. 11 reproduces part of a somewhat oblique vertical section of a 
sporophyll. Here both the sporangia appear at once; toward the 
right and between them lies the separating partition containing 
the fibrovascular strand and its associated transfusion elements. 
Toward the left the transfusion cells can be distinguished, passing ~ 
directly into elements with much more openly reticulated walls, 
the mechanical cells. Fig. 18 is a somewhat diagrammatic repre- 
sentation of the anatomical situation in the sporangium of Pseudo- 
larix. The tracheary strand comes into the sporophyll and passes 
outward, giving off a shorter or longer dorsal branch. Abaxially 
it spreads out into a mass of transfusion elements which are con- 
nected with the more coarsely reticulated cells, constituting the 
mechanical sheath of the microsporangium. Nearly opposite the 
point of contact of the vascular bundle with the upper wall of 
the sporangium lies the stomium. The sporophyll ends in a sharp 
upwardly directed apex, comparable to the less well developed 
similar structure in Ginkgo. 
In the Pineae the thin wall of the pollen sac has brought with it 
such a degree of degeneracy that the topographical relations, seen 
clearly in the Abietineae, can no longer be discerned. The epi- 
dermal layer of the microsporangium is apparently in all cases 
fibrously thickened, and in this respect differs from the annulus 
found in the remaining Pteropsida. In the araucarian conifers, 
which are by many regarded as a primitive subtribe of the Conif- 
erales and more nearly related to the Cordaitales than any other 
subtribe, significantly enough, the mechanical layer is reduced to 
the epidermis and has no connection whatever with the fibrovas- 
cular system. The same statement is true of the remaining sub- 
tribes of the Coniferales other than the Abietineae, which in respect 
