LYCOPODIUM SPOROPHYTE 283 



its continuity may be traced up to the apical cone, as 

 a bright-looking strand of formative tissue consisting 

 chiefly of prosenchymatous elements (plerome or pro- 

 cambium), while the formative tissue of the cortex 

 external to it is more typically parenchymatous (peri- 

 blem) : it is limited by a layer of cells, which, though 

 not clearly defined towards the extreme apex, may be 

 recognized as the dermatogen. 



The conical apex itself consists of a dome-shaped 

 mass of meristem : the layer of dermatogen, which may 

 be recognized at the base of the cone, may be followed 

 up nearly to the apex, but there loses its identity, the 

 extreme apex being occupied, at least in the more 

 bulky examples, by a group of initial cells (stated by 

 Strasburger to be three in L. Selago), which divide by 

 both anticlinal and periclinal walls. Compare this on 

 the one hand with the structure of the apex of the 

 stem of Phanerogams (p. 80), and on the other with 

 that seen in the Ferns. 



Observe further that the development of the 

 leaves begins by the outgrowth and division (both 

 anticlinal and periclinal) of groups of cells, which con- 

 stitute multicellular protuberances : these have at first 

 an apical growth, which soon ceases, the further growth 

 being basal and intercalary. 



The origin of the branches may further be observed 

 in these preparations : it will be seen that they arise 

 in this species below the apex of the main axis, and 

 laterally upon it ; the branching is thus monopodial, 

 not dichotomous. 



VIII. Cut transverse sections of one of the thick 

 roots: mount as before, and observe that they re- 



