Cell-Pedigrees 87 



thence of a continuation of the main-lines. But this is 

 not the case to the same extent for all branches as we shall 

 soon see. 



In our picture two important parts are still lacking, 

 one of them being the roots, the other the organs of re- 

 production. The roots need only briefly be mentioned. 

 They grow by means of apical cells, the same as the 

 shoots, and are present in the lateral buds before the 

 latter arise from the leaf whorls. As a rule, every bud 

 at first forms only one root, which develops from an inner 

 cell, situated on its under side. This cell becomes the 

 apical cell of the young root. Therefore, in the genea- 

 logical tree every root, as well as every shoot, is repre- 

 sented by a branch with its numerous twigs. But since 

 the roots never bear leaf -buds, as in many ferns and pha- 

 nerogams, and therefore never produce any organs of 

 reproduction, they are always only sterile branches of the 

 pedigree. 



In the case of Equisetum arvense this is the fate of 

 by far the greater portion of the branches of the cellular 

 pedigree. Because here only the pale, yellow shoots of 

 the later years, without chlorophyll, are selected for re- 

 production. Thus, here too, we distinguish sterile and 

 fertile branches. 



At the apex of the fertile shoots stand the sporangia 

 in crowded spikes of four- to six-sided shields, which have 

 their stems in the center. Every one of these corres- 

 ponds in its origination to a tooth of a leaf-whorl. Hence, 

 the cell-pedigrees of the individual shields can be derived 

 in a similar manner from the apical cell of the shoot, as 

 in the vegetative part ; and in the same way the origin of 

 each single spore can be traced back to it. These lines 

 again we call branches, while all the lines leading to the 



