THE YOUNG SPOROPHYTE 



153 



THE STEM OF THE YOUNG SPOROPHYTE. 



The stem apex projects very little or not at all, and occupies but a limited area 

 close to the base of the cotyledon. Its outer surface is nearly horizontal, except in 

 Angtopteris, where it is generally strongly inclined (fig. 134). There probably is 

 always a single apical cell. Segments are cut off from the sides, and very often also 

 inner segments, where the base of the apical cell is truncate. The lateral segments 

 also have, cut off from their inner faces, cells which contribute to the growth in length 

 of the stem, which remains, however, very short in the young sporophyte, the leaves 

 being very much crowded together. As we have already stated, no central cylinder 

 properly belonging to the stem can be demonstrated at this time, all of the procambial 



cat 



Fig. 135. — Young sporophyte of Angtopteris. 



A. Stem apex, showing single apical cell. X150. 



B. Second leaf, /",of same sporophyte. 



Fig. 136. 



A. Nearly median section of a young sporophyte of KauJjussia. B. Another section of same, showing continuity of bundles ot 

 /^, second leaf; m, mucilage ducts; sr, stem apex; ^r, game- cotyledon and root, 



tophyte. X about 20. C. The stem apex. 



tissue belonging either to the cotyledon or to the root. In the older embryo of 

 Marattia douglasti the apex of the stem (fig. 139, 5) is occupied by a group of rela- 

 tively large cells, which at first sight seem to be pretty much alike; but a careful 

 examination of these makes it probable that one of them may be considered as the 

 real initial cell. This, in cross-section, appears almost square and shows a fairly 

 regular segmentation. While it must be said that the segmentation is not so regular 

 that one can assert without question that all of the meristem is really due to the 

 activity of a single cell, I believe that this is probably the case. 



My own investigations of the stem apex in Angtopteris have led to the conclusion 

 that there is a single initial cell here also in the young sporophyte, although Farmer 



