igi 5 ] 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 occidental is (tigs. 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 Ckamaecyparis 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. At a little later stage 



