Ig15] AASE—M EGASPOROPHYLLS OF CONIFERS 291 
the same orientation of parts as the latter bundle. A fact to be 
noted in the further course of the bundles is that some of the lower 
scale bundles extend into the bract, though not as far as the bract 
bundle. 
The ovulate strobilus of Thuja occidentalis (figs. 71-89) con- 
sists of about five decussate pairs of sporophylls. The two lower 
pairs are sterile, the third may have only one ovule to each sporo- 
phyll, the fourth two ovules to the sporophyll, and the fifth is 
sterile. The tissues of the bract and scale are so closely welded that 
it is impossible to distinguish one from the other except at the very 
tip. In the upper fertile pair of sporophylls the vascular supplies 
to bract and scale are distinct in origin. The supply of the first 
arises as one bundle at one side of the continuous gap; that of the 
latter as two bundles, one at each side and at a higher level. The 
bract bundle does not divide; the scale bundles give rise to numer- 
ous bundles, a few of which become inverted and lie near the dorsal 
side of the sporophyll; the majority, together with the bract bundle, 
form an irregular lower row of inverted bundles. In the two sterile 
pairs at the base, the bract and scale supply have their beginning as 
one bundle at one side of the long gap. This bundle soon drops 
into three, the median one supplying the bract, the two lateral the 
scale. The further course is as described before for the upper 
fertile sporophyll. In the lower fertile sporophyll is found a com- 
bination of the two methods of bundle origin mentioned. One 
of the scale bundles rises separately, but the other is combined with 
the bract bundle and rises at a lower level; it later separates 
from the bract bundle. The sterile tip pair of sporophylls receives 
the last two bundles of the strobilus axis. One bundle goes to 
each sporophyll, and drops into three bundles which divide further. 
The strobilus of Chamaecyparis Lawsoniana (figs. 90-104) 
consists of about four pairs of sporophylls. In the cone repre- 
sented in cross-section (figs. 100, 101), one of the lowest sporophylls 
has one lateral ovule, each of the sporophylls of the second pair 
two lateral ovules, and each of the third pair one median ovule; 
the fourth pair is sterile. In the early free-nuclear stage the 
scale is apparent only as a slight elevation on the dorsal side of the 
bract, which at this stage is almost straight. Ata little later stage 
