498 



BOTANICAL GAZETTE 



[JUNE 



distance below the tip of the primary axis (fig. n), in which the 

 tip of the primary axis has also begun its renewal of growth for 

 the third successive season. No case was found in which it was 

 known that a terminal primary shoot later became functionally 

 vegetative; but in view of the occasional behavior of the primary 

 shoot as a leafy shoot, it is very possible that a terminal primary 

 shoot may again become vegetative in function. 



Figs. 12-18. — Series at different levels showing vascular supply from leafy shoot 

 to primary shoot: fig. 12, vascular cylinder of leafy shoot; fig. 13, trace to fertile leaf 

 and formation of vascular strands to primary shoot; fig. 14, vascular strands for 

 primary shoot separated from main cylinder, showing branch gap; fig. 15, main axis 

 cylinder closed with primary axis cylinder and bundle of fertile leaf farther removed; 

 fig. 16, primary axis cylinder closed; figs. 17, 18, bundles to lower scales of primary 

 shoot, first pair being normally transverse, as shown, remainder usually spiral with 

 occasionally a second transverse pair, as in fig. 18; X24. 



Vascular features. — Strasburger (35) was the first to 

 describe the vascular supply of the primary shoot of T. baccata, 

 and it is essentially the same in T. canadensis. The primary shoot 

 receives two bundles from the axis of the leafy shoot (figs. 12-15). 

 These bundles meet at their edges (fig. 16) and form a complete 

 vascular cylinder, which then gives off traces to the lateral scales 

 (figs. 17-20). At the level of the fertile scale the cylinder organizes 



