22 Bafnes. — The Morphology of Agathis australis . 
has been somewhat obscured by simplification through fusion. Yet such 
a condition is evident in the presence of the two series of vascular strands — 
the lower normally oriented, the upper with reversed xylem and phloem 
—and by the two free apices on the fertile structure. Both ways in which 
coalescence and reduction can occur have been seized upon. The resulting 
strobilar element is in one case composed chiefly of the tissue of the fertile 
scale, the bract having nearly disappeared ; and in the other of that of the 
bract, the scale being barely represented. The former is much more com- 
monly found. Sequoia forms a good example. In this genus the scale has 
enlarged and folded down, enclosing and obscuring the small bract. This 
is evident externally by the position of the bract tip, which projects like an 
umbo centrally from the scale, internally by the vascular supply (Text-figs. 
79-81). The entire supply arises together as a cylinder. Soon the two series 
are formed. That for the bract is a small median bundle. The strong 
inverted series almost surrounding it is that of the fertile scale. Lateral 
portions of a false lower series are formed by upfolding from the wings of 
the enlarged scale. 
As examples of bracteal enlargement at the expense of the scale, 
Cunninghamia and two species of Athrotaxis may be cited. Externally the 
presence of the seminiferous scale is evinced in Cunninghamia only by a collar- 
like projection from the region of ovular attachment (Text-fig. 85). In 
Athrotaxis laxifolia^ Hook., it is represented by a rounded cushion-like mass 
upon the prominent bract (Text-fig. 83), whereas in A. selaginoides all ex- 
ternal evidence of a scale has disappeared. That these vestiges must represent 
the ovuliferous scale of the Abietineae is evident from the undoubted origin 
of the Taxodineae, from the occurrence within the tribe of all transitional 
stages, as well as from the evidence of vascular anatomy given below. 
Only in the Araucarians and the Podocarps has the double nature of 
the female strobilar scale been questioned. Some investigators claim that 
the megasporophylls in these groups are simple in nature, being merely 
fertile bracts, strictly homologous with the microsporophylls — and therefore 
not at all of the same nature as those of the Abietineae. If such is the 
case, both simple and compound strobili occur in the Coniferales. This is 
a vital point and concerns deeply the unity of a group which otherwise 
seems to be clearly a natural one. 
The writer will try to show that the strobili of the Abietineae and the 
Araucarineae are homologous — that those appearances suggesting a simpler 
origin of the fertile scale are due to nearly or quite complete coalescence and 
great reduction. 
Even within themselves the Araucarineae show a complete series from 
a form with strobilar units of a distinctly double nature to one most simple 
through reduction. Further, exactly parallel evolution has taken place in 
the Taxodineae. The apparently simple sporophyll of the Podocarpineae 
