igi S ] AASE—MEGASPOROPHYLLS OF CONIFERS 285 



bundles soon unite into one, so that four bundles in all with xylem 

 facing result; the lower passes undivided to the end of the bract, 

 the three remaining spread out and give rise in the scale to a row 

 of inverted bundles, seven or more in P. maritima, twelve or more 

 in P. Banksiana. No branches are seen to bend toward either of 

 the two inverted ovules. Below the middle of the strobilus the 

 uppermost one or two bundles, as the case may be, originate near 

 the lower scale bundles or become united with the latter so that the 

 scale supply starts as two bundles. One of the two bundles soon 

 divides, so that four bundles including that of the bract result; 

 the subsequent course in the appendages is as described before. 

 In the lower sporophyll, the scale supply originates as one or two 

 bundles very near the bract bundle. In the lowest sporophylls 

 the bract and scale supply originates as a single bundle at the base 

 of the gap. In either case there is a subsequent separation into 

 four bundles which supply their respective appendages as before 

 described. In this region of the strobilus the four bundles remain 

 closer together in their course through the cortex than is the case 

 in the upper. In P. Banksiana the phloem is continuous around 

 the four xylem strands, which except for a few parenchyma cells 

 would form a solid xylem strand. Near the base of the strobilus, 

 in this species, where the sporophyll supply begins as a single 

 bundle, the xylem creeps around its protoxylem as a pivot and the 

 phloem about the xylem, so that a concentric bundle results. 

 On nearing the appendage the bundle drops into four. In this 

 species the gaps are small, owing to a shortening of the strobilus axis. 

 In both species the sporophyll supply takes a diagonal downward 

 course through the cortex in the lower part of the strobilus, in 

 contrast to the diagonal upward course taken near the tip. This 

 is also likely due to a shortening of the strobilus axis and a conse- 

 quent crowding of the appendages. 



For the sake of comparison, the anatomy of a young vegeta- 

 tive shoot was investigated. In P. maritima and P. Banksiana 

 (figs. 30-35), whether the bud is to give rise to a spur shoot or a 

 long branch, a single bundle springs from the base of the cylinder 

 gap and supplies the bract, while two other bundles, one at each side 

 of the gap, supply the hud. The bud bundles increase in size and 



