494 



MOSSES AND FERNS 



CHAP. 



kinds and arranged in four rows, as in most species of Selagi- 

 nella. The branching of the stem is either dichotomous or 

 monopodial. The roots, which are borne in acropetal succes- 

 sion (Bruchmann found also in L. inundatum adventive roots), 

 branch dichotomously, hke those of Isoetes. The sporangia 

 are borne singly, in the axils of the sporophylls, which may 

 differ scarcely at all from the ordinary leaves (L. selago, L. 

 hicidulum), (Fig. 287), or the sporophylls are different in 

 form and size from the other leaves and form distinct strobili, 



Fig. 287. — Lycopodium selago. A, Longitudinal section of the stem apex, X120; F, F, 

 young leaves; i, i, initial cells; PI, plerome; B, surface view of the stem apex, 

 showing the group of initial cells, X260; C, longitudinal section of the root- tip; d, 

 dermatogen; Pb, periblem; PI, plerome; Cal, calyptrogen; h, h, root-hair initials, 

 X 120 (all the figures after Strasburger). 



which are often borne at the end of almost leafless branches 

 (Fig. 282). 



None of the investigated species of Lycopodium show a 

 definite initial cell at the apex of the stem, and Treub ( (2), V) 

 was unable to determine positively whether such a one exists in 

 the embryo. In L. phlegmaria he describes and figures, em- 

 bryos, where a single prismatic apical cell is apparently pres- 

 ent, but in others the presence of such a cell was doubtful, and 

 in L. cernmmi in no case did he find any evidence of a single 

 initial. 



The vegetative cone of the mature sporophyte is usually 



