560 BOTANICAL GAZETTE [may 



cell within a segment; and that the entire segment rises abruptly 

 above the plane of the apex of the stem. 



In connection with the investigation of the origin of the axillary 

 buds, the apical region of B. obliquum has been examined, and 

 the results will be given briefly. As shown by figs. 13 and 14, 

 the apical cell is a triangular pyramid, with three cutting faces. 

 The first division of a segment is by a periclinal wall, as stated 

 for B. virginianum by Campbell; the further divisions are 

 irregular. 



While the limits of the various segments cannot always be 

 exactly defined, it seems certain that each segment gives rise to a 

 leaf; hence one segment is cut off each year. Fig. 13 represents 

 a transverse section through the apical region of a plant collected 

 early in April; the first segment was cut off during the preceding 

 year and has divided transversely. In the second year, irregular 

 divisions, both longitudinal and transverse, take place with the 

 segment; at the end of the year, the segment consists of 6-15 cells. 

 During the third year, this irregular division continues; but there 

 is little or no extension above the plane of the apex. At the 

 beginning of the fourth year, the segment begins a much more 

 rapid growth and rises abruptly above the plane of the apex, as 

 described by Brltchmann; at about the same time, an apical cell 

 is recognizable within the segment, and the further growth is defi- 

 nitely apical. It is evident that while the entire segment takes part 

 in the initial growth, the leaf is formed from only a part of the seg- 

 ment; the remainder of the segment builds up the stem tissues. 

 By the end of the fourth year, the leaf has become a hemispherical 

 mass which has grown forward and upward, and its forward margin 

 extends considerably beyond the apical cell of the stem (fig. 14). 

 Early in the fifth year, the fertile spike makes its appearance. It 

 is first recognized as an apical cell on the forward side of the apical 

 cell of the leaf; by the end of the year, it has produced a well 

 defined knoblike structure. During the sixth year, both the fertile 

 and sterile portions of the leaf develop rapidly. In the summer of 

 the seventh year, this leaf breaks through the base of the envelop- 

 ing older leaf, and the spores are shed in September. The fertile 

 spike then withers, but the sterile portion of the leaf persists 



