84 Cell-Pedigrees 



before ns.^ The fertilized egg-cell in the archegonium 

 begins its growth by divisions, the first of which stands 

 nearly at right angles to the axis of the archegonium ; 

 this is followed by two walls at right angles to this and to 

 themselves. From the lower octants develop the root and 

 the foot of the young sporophyte, the latter by the for- 

 mation of a small-celled tissue body due to continued di- 

 visions. These branches of the pedigrees are thus ended. 

 From one of the upper octants of the embryo the apical 

 cell of the first shoot originates, the other octants partici- 

 pate in the formation of the annular thickening which 

 represents the first leaf -whorl, and thus soon end their 

 growth, after continued divisions. 



The growth of the first, as well as of all successive 

 shoots is dominated by the apical cell. The latter occu- 

 pies the apex of the shoot, its upper cell-wall is spheri- 

 cally arched, while downward it is limited by three almost 

 plane walls. It has, therefore, the shape of an inverted 

 three-sided pyramid. It divides only by walls which run 

 parallel to the three sides of the pyramid ; every detached 

 piece is called a segment. By numerous divisions, the 

 three successive segments, parallel to the three sides 

 of the pyramid, always form an internode with a leaf- 

 whorl at its upper end. The whole shoot, therefore, 

 consists of sections each of which owes its origin uO a 

 segment whorl of the apical cell. 



The apical cell, therefore, evidently represents the 

 main stem of our pedigree; every segment corresponds 

 to a branch. During the development of the shoot, and 

 consequently, during the first year of vegetation of the 



^Illustrations of the required stages of development are found in 

 Goebel, K. Grundziige der Systematik imd Spesiellen Pflansenmor- 

 phologie pp. 286-304. 1882. 



