Hill and de Fraine. On the 
216 
this feature may prove to be very obscure in some species, for the fission 
only requires to be extended a very little further to completely divide each 
seed-leaf into two. 
Araucaria brasiliensis. 
The seedling of this species differs from that of A. Cunninghamia in the 
following more or less important features : — it is hypogeal ; the cotyledons 
are two in number, unbranched and rather massive ; the hypocotyl is 
relatively much thicker. The internal structure also differs ; each cotyledon 
has more vascular strands, five, six, or seven, instead of four as in A. Cunning- 
hamii ; the resin ducts are more numerous and are not restricted to the peri- 
pheral regions. The presence of stomata and transfusion tracheides are points 
of similarity to A. Cunninghamii , and so also is the character of the bundles 
which are endarch and collateral throughout the whole length of the seed-leaf. 
Transition. 
Series A. Although in the more distal parts of the cotyledons the 
vascular strands may number more than six, six enter the axis, the reduction 
being effected by the fusion of certain of them. In the hypocotyl the most 
laterally placed bundles fuse with their neighbours so that there are eight 
traces, arranged in two groups of four (Diagram 11, Figs. 1-5). At a lower 
level each group of four bundles fuse in pairs, although, in the seedling now 
being described, this was masked to some extent by the presence of well- 
developed plumular traces. 
In the upper region of the hypocotyl the plumular traces form an unin- 
terrupted vascular cylinder enclosing a mass of parenchymatous tissue 
(Diagram 11, Fig. 3) ; at a lower level this vascular ring breaks up into four 
parts, two of which are situated in a plane at right angles to that of the 
cotyledons and the others are placed one in each gap (Diagram 11, Fig. 4). 
The disposition of the bundles obtaining at the commencement of the transi- 
tion is illustrated in Diagram 11, Fig. 4, from which it may be seen that the 
cotyledon-traces are arranged in two main groups (c and c 1), each group 
being further divided by an intervening plumular strand (p and p 1) ; there 
are thus four pairs of seed-leaf-traces, the individuals of one pair of which 
have joined together. The space between the two large groups of four is 
bridged by the elongated masses of epicotyledonary vascular tissue. 
Tracing these structures downwards, the cotyledonary traces fuse in pairs, 
move inwards, and join on to the large masses of plumular vascular tissue 
(e and e 1). A comparison of Figs. 5, 6, and 7 in Diagram 11 shows that 
the details of this movement are not precisely the same on each side of the 
axis. The cotyledon-traces c , on the left side, fuse with the intervening 
plumular strand /, and forming a broad band of vascular tissue which, how- 
ever, soon separates into two parts, one half joining with e and the other 
portion with e 1. The strands, on the right side, c 1, join up with e and e 1 
