159 



THE APICAL GROWTH. 



Lang foiuid that the apical cell in the 0. lyendulum was a 

 four-sided pyramid, and not tetrahedral, as in 0. vnhjatum; 

 the writer's observations confirm this. In longitudinal section 

 (Figs. 47 — 68) the apical cell appears triangular with a fairly 

 regular segmentation, but there is also active division in the 

 adjacent tissue and apparently the segmentation of the apical 

 cell is not very rapid. Cross sections show the apical cell to 

 be approximately four-sided (Fig. 67), but the sides are not 

 always of equal length, and occasionally it is almost triangular 

 in outline. Possibly it may be that in some cases, as in 0. 

 vulgahim, it is tetrahedral. There seems to be no absolute rule, 

 liowever, as to the succession of divisions in the young segments. 

 A more or less definite superficial layer arises from the first 

 periclinal divisions, l)ut anticlinals succeed rapidly. 



THE SEXUAL ORGANS. 



There is much difference in the time of the appearance of 

 the sexual organs. Sometimes there are none at all near the 

 apex, while in some instances the young sexual organs can be 

 recognized in the second youngest series of segments (Fig. 68). 

 The mother cells of the young archegonia and antheridia are 

 much alike, and it is not easy to distinguish them apart in 

 their earliest phases. The mother cell is cut out by a series 

 of vertical intersecting walls in the outer cell of the young 

 segment. While in a general way the young reproductive organs 

 arise in acropetal succession there may also develop later 

 intercalary ones. The number is often very great, but some- 

 times they are formed rather sparingly; although both arche- 

 gonia and antheridia are usually mingled somewhat indiscrimi- 

 nately, it is not uncommon for one or the other to predominate 

 and some branches may be almost exclusively devoted to the 

 formation of antheridia. The latter are very large, — probably 

 larger than in any other Pteridophyte, and are easily visible 

 to the naked eye. 



