VIII 



THE PTERIDOPHVTA—OPHIOGLOSSACE.E 



231 



in the species of the temperate regions, as the growth continues 

 uninterruptedly throughout the year. The real apex of the 

 stem forms an inclined nearly plane surface, slightly raised in 

 the centre, where the single apical cell is placed (Fig. 115, A, 

 B). This cell is by no means conspicuous, and not always 

 readily found, but probably is always present. It has the 

 form of an inverted three-sided pyramid, but the lateral faces 

 are more or less strongly convex, and the apex may be trun- 

 cate. From the few cases 

 observed it is not possible 

 to say whether in addition 

 to the three sets of lateral 

 segments basal segments 

 are also formed, but it is 

 by no means impossible that 

 such is the case. According 

 to recent investigations of 

 Rostowzew ^ the apical cell 

 of the stem of Ophioglossiim 

 vulgatuin shows consider- 

 able variation, and may be 

 either a three or four-sided 

 prism, i.e. it apparently also 

 may have the base truncate. 

 Holle's ^ description agrees 

 with this except that he 

 states that he always found 

 the cell pointed below, not 

 truncate. The segments 

 cut off from the lateral 

 faces are large, and the 

 divisions irregular. They 

 are apparently formed in 



very slow succession, and the irregularity of the succeeding 

 divisions in the segments themselves soon makes it impossible 

 to trace their limits. Each segment apparently gives rise to a 

 leaf, but this is impossible to determine with certainty. The 

 first wall in the young segment probably divides it into an 

 inner and outer cell, but the next divisions could not be deter- 

 mined positively. Probably, as in Botrychium, the outer cell is 

 ^ Rostowzew ( I ), p. 451. - HoUe (i). 



Fig. 114. — Ophioglossu7ti pendiihi7n {'L,.'). A, Median 

 longitudinal section of stem apex, X 4 ; x, the 

 growing point; B, young sporophyll, X2; sp, 

 the sporangiophore ; C, an older leaf, showing 

 the venation, X2. 



