I9 o8] THI ESSEN— DIOON EDULE 365 



spiral turns is more slender and folds over the next inner leaf more 

 than does its mate (fig. 7). It will be observed that the girdle which 

 is destined for that side of the leaf generally describes a longer curve 

 through the cortex than the one destined for the other side. The 

 phenomenon of girdling will become clearer when illustrated by a 

 specific case. In fig. 6, taken from a young seedling, L I} L a , L 3 , 

 and L 4 represent the first, second, third, and fourth leaves or primor- 

 dia; L\, L\, L\, L\, the four strands of the first leaf; L\, L$, L\, L 4 , 

 the strands of the second primordium. L\ is the longest girdle of the 

 first leaf and has its origin at the protoxylem group px 1 , on the side 

 directly opposite the leaf to which it belongs, ascends for a short 

 distance, then turns outwardly into the cortex and describes a wide 

 horizontal curve, enters the longer and more slender edge of the 

 leaf base, and ascends in the petiole in the dorsal left-hand portion, 

 branching repeatedly in its further course. Trace Lf leaves the cen- 

 tral cylinder near the protoxylem group px 4 , ascends a short distance, 

 runs upwardly and outwardly into the cortex, describes a horizontal 

 curve in the opposite direction, enters that side of the leaf having the 

 shorter sheathing base, and ascends in the dorsal or adaxial portion 

 of the petiole, where it branches repeatedly in its further upward 

 course. From this it will be seen that the leaf trace L\ pursues a longer 

 course than trace L 4 . Trace L\ has its origin near the protoxylem 

 group px 3 , to the left, ascends for a short distance, runs out into the 

 cortex, makes a very slight horizontal curve (almost direct) into the 

 leaf base, running outwardly, and then ascends on the ventral or 

 abaxial left-hand portion of the petiole without further branching. 

 Trace L\ has its origin near the protoxylem group px 4 , ascends for 

 a short distance, runs outwardly (gradually ascending) with a slight 

 curve into the leaf base, and finally ascends in the ventral or abaxial 

 right-hand portion of the petiole without further branching. It will 

 be seen that in the case of the two inner strands L\ makes a girdle of 

 about oo°, while trace L\ is approximately direct. 



About the same condition occurs in the traces of the second leaf. 

 Trace L\ has its origin to the left and near the protoxylem group 

 px 3 , ascends vertically for a short distance (but farther than the 

 strands of L t ), runs a short distance outwardly into the cortex and 

 then makes a wide horizontal sweep, enters the leaf base on that side 



