1912] STOLAND— SPIKE OF BOTRYCHIUM 527 



the vascular strands relative to the supply of the abortive spike. 

 The vascular strands are all of the concentric type throughout the 

 aerial part. About 8 cm. below the abortive spike the leaf trace 

 consists of three pairs of strands (fig. 3, d, e, f), one large lateral 

 pair (fig. 3, d), and two pairs on the abaxial side (fig. 3, e, /). One 

 of the pairs (fig. 3, /) soon unites with the abaxial margin of the 

 lateral strands (fig. 4). The second pair (fig. 3, e) remains free to 

 within 1 cm. of the abortive spike, where it also unites with the 

 abaxial margins of the lateral strands (fig. 6). The vascular 

 strands of the abortive spike originate about 8 cm. below the 

 point where the spike leaves the petiole. The adaxial arms of the 

 lateral strands become hooked (fig. 3) and soon a curved strand 

 (figs. 3-7, a) is cut off so that a gap is left in the sides of the leaf 

 traces (figs. 4-6, g). From each side of these gaps a small strand 

 breaks off to supply the abortive spike (figs. 4-8, b, c). The out- 

 line of these strands appears below the gap, so that they really 

 originate from its base (fig. 3, b). 



There are then four strands, that is two on each side, that supply 

 the abortive spike. They adhere to the sides of the gap for some 

 distance, but finally break off, one 5 cm. (figs. 4, 5, b), the other 

 about 2 cm. (fig. 7, c) below the abortive spike. From this point 

 they remain as separate strands running along the gap and finally 

 enter the abortive spike (figs. 9, 10, b, c). The gaps in the lateral 

 leaf traces close about 4 mm. below the abortive spike (fig. 8). At 

 about this point the two lateral traces (fig. 8, d) each divide into 

 two equal strands. The adaxial strands thus formed are hooked 

 (figs. 8-10, h). These adaxial hooked strands each divide into 

 two equal parts (fig. 12, A' \ b f ) of which the outer pair (b') diverge 

 to pass out to the pinnae (figs, n-15, b f ). Another pair of strands 

 (figs. 13, 14, c f ) arise from the adaxial margin of the lateral strand 

 (figs. 13, 14, d), so that each pinna has two strands. Where these 

 strands (c f ) leave the leaf trace the gap becomes closed, strand a' 

 uniting with strand d. The leaf trace above the origin of the first 

 pair of pinnae consists of two lateral strands (fig. 15, d). By a 

 study of figs. 3-15 it will be seen that the same series of changes 

 occurs in the origin of the vascular supply of the sterile pinnae as 

 for the abortive spike. 



