PTERIDOPHYTA 



307 



The development of the organs of the young sporophyte is slow, and there is 

 a good deal of difference in this respect among the several species which have 

 been investigated. In L. cernuum and the related L. inundatum, there is 

 developed a body, the "Protocorm," which gives rise secondarily to the other 

 organs. In the other species the embryo shows a division into two tiers, of 

 which the one next the suspensor becomes much enlarged and forms the foot 

 (Fig. 272) ; the terminal one gives rise to the other organs of the embryo. A 

 single cotyledon is present in L. cernuum and L. phlegmaria, but in L. clavatum, 

 and other European species, Bruchmann states that the primary leaves are 

 opposite, as they are in Selaginella. In these species, also, the first root to 

 develop is endogenous, instead of exogenous as described by Treub for L. cer- 

 nuum, in which, moreover, the stem remains short, and numerous leaves are 

 formed before the root develops. Where the sporophyte is developed under- 

 ground, as in L. clavatum, the leaves remain small and scalelike (Fig. 269, B). 



F 



FIG. 273. Lycopodium selago. A, B, stem-apex (X 260). C, apex of root (X 120). 

 A, C, longitudinal sections. B, Cross-section, i, i, stem-initials; PI, plerome; 

 Pb, periblem; d, epidermis; h, root-hair initials; Cal, calyptrogen. (After 

 STRASBURGER.) 



Several embryos are formed upon the same gametophyte, and the sporophyte 

 remains for a very long time dependent upon the gametophyte. This and the 

 slow development of the organs and tissues all point to the very primitive char- 

 acter of Lycopodium. 



THE MATURE SPOROPHYTE 



In most species of Lycopodium (Fig. 270) the small crowded 

 leaves are arranged spirally about the axis, which branches freely. 

 The branching may be either monopodial or dichotomous. In a few 

 species e.g. L. complanatum the leaves are closely imbricated, and 

 arranged in four rows, much as they are in most species of Selagi- 

 nella. The roots branch dichotomously. The leaves are always very 

 simple in structure, with a single median vascular bundle. 



